# How does Facebook know I know these people? **URL:** \ **Category:** Factual Questions\ **Created:** [July 9, 2009, 3:46pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462 "2009-07-09T15:46:32Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [July 9, 2009, 3:46pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/1 "2009-07-09T15:46:32Z")
Facebook has started recommending people to be friends with me who I have in fact interacted with–but never on Facebook. We have no mutual Facebook friends. Yet somehow, Facebook makes a connection between us. Examples include people whose blogs I’ve posted on, and people who I’ve emailed about papers they’ve written. How on earth could Facebook connect me with these guys? ---
**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\ **Post date:** [July 9, 2009, 4:16pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/2 "2009-07-09T16:16:58Z")
I am curious too. Facebook recently suggested a Doper to me as a friend. It just so happens that he and I are pals on the board here, are the same age and are in the same industry. But AFAIK neither of us mention the SDMB on our profiles and he doesn’t list any work info. I do have a (very short - 2 people) “friend list” titled SDMB…could be that he has one too. But, if that’s the criteria they are using to match us up, I find it odd that NONE of my other friend suggestions have ever been Dopers. They are all people from school. ---
**Author:** ![bit24sh0cker](https://avatars.discourse-cdn.com/v4/letter/b/b5ac83/32.png) [@bit24sh0cker](https://boards.straightdope.com/u/bit24sh0cker)\ **Post date:** [July 9, 2009, 4:18pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/3 "2009-07-09T16:18:17Z")
I think when you give access to your email address program - they read your emails. ---
**Author:** ![CaveMike](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cavemike/32/16379_2.png) [@CaveMike](https://boards.straightdope.com/u/CaveMike)\ **Post date:** [July 9, 2009, 4:38pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/4 "2009-07-09T16:38:26Z")
> [@bit24sh0cker](#): > > I think when you give access to your email address program - they read your emails. In my case, I have never given FB this access. I think FB is now doing 6-degrees of separation like in LinkedIn. It knows you have friends in-common eventually. ---
**Author:** ![StarsApart](https://avatars.discourse-cdn.com/v4/letter/s/ecc23a/32.png) [@StarsApart](https://boards.straightdope.com/u/StarsApart)\ **Post date:** [July 9, 2009, 4:41pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/5 "2009-07-09T16:41:54Z")
I doubt they’re “reading your emails.” They’re accessing your contact list - or rather, since you haven’t given them access to your contacts, they are accessing the contact lists of those who have given them access. You may be on their lists for whatever reason, so they connect you to that person, which then connects you to others in their contact list and so on and so forth. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [July 9, 2009, 4:48pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/6 "2009-07-09T16:48:09Z")
Job, school, friends, email address, email contacts and names you have searched on all create possible links to other people. ---
**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\ **Post date:** [July 9, 2009, 4:50pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/7 "2009-07-09T16:50:09Z")
Facebook doesn’t access your contact list unless you specifically give them access. And when you do grant permission, they don’t send notices to people on the list; that’s up to the person who gave them access. In other words, if you grant access, Facebook lists people on both Facebook and your list and asks which ones you want to contact. They don’t do it themselves. Leaving the contact lists aside, Facebook will suggest people who belong to the same network as you and who show similar interests. I get some suggestions by people I know but who have just joined the network so there are no friends in common. I’m sure that’s because of interests. ---
**Author:** ![mazinger\_z](https://avatars.discourse-cdn.com/v4/letter/m/5f9b8f/32.png) [@mazinger\_z](https://boards.straightdope.com/u/mazinger_z)\ **Post date:** [July 9, 2009, 5:02pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/8 "2009-07-09T17:02:38Z")
I think it’s weird. I’ve gotten, as friend suggestions, two ex-gfs, my accountant’s kid, some people I haven’t seen since grade school, and my friend’s mom. The email account I use for facebook is a dummy account with no contacts. The only emails that come to that account are literally only facebook emails (i.e. facebook alerting me that someone read something or posted something, etc.) I don’t even use my own picture. ---
**Author:** ![Bijou\_Drains](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bijou_drains/32/2814_2.png) [@Bijou\_Drains](https://boards.straightdope.com/u/Bijou_Drains)\ **Post date:** [July 9, 2009, 5:06pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/9 "2009-07-09T17:06:15Z")
I don’t really use facebook but I do list my high school on it. I know some of the people they suggest be my friends are from my high school, maybe a lot of them are. ---
**Author:** ![Swallowed\_My\_Cellphone](https://avatars.discourse-cdn.com/v4/letter/s/9d8465/32.png) [@Swallowed\_My\_Cellphone](https://boards.straightdope.com/u/Swallowed_My_Cellphone)\ **Post date:** [July 9, 2009, 5:27pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/10 "2009-07-09T17:27:11Z")
Most of my recommendations come from people who are associated with guys on my baseball team. Occasionally I’ll recognize someone in the “recommended friends” list and I can almost always track it back to someone from baseball or a couple people I used to go kayaking with. It’s almost always only one degree of separation: a friend of a friend. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [July 9, 2009, 5:33pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/11 "2009-07-09T17:33:39Z")
I suspect that some of these people have given Facebook access to their email accounts, and that it’s suggesting them to you if they have your email address. Otherwise, I have no explanation for how it knew to recommend me a couple people who showed up. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [July 9, 2009, 5:50pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/12 "2009-07-09T17:50:58Z")
Right,\*\* ultrafilter\*\*. You might not grant access to email contacts, but think of all your contacts and how they might give access to their lists (which include you!). ---
**Author:** ![otorophile](https://avatars.discourse-cdn.com/v4/letter/o/3ab097/32.png) [@otorophile](https://boards.straightdope.com/u/otorophile)\ **Post date:** [July 9, 2009, 6:08pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/13 "2009-07-09T18:08:08Z")
Seeing my high school teacher as a person I may know was fairly strange. I use an ad blocker, so I’m curious: are ads on facebook well tailored to what you write about yourself on your profile page? ---
**Author:** ![Mister\_Rik](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mister_rik/32/491_2.png) [@Mister\_Rik](https://boards.straightdope.com/u/Mister_Rik)\ **Post date:** [July 9, 2009, 6:20pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/14 "2009-07-09T18:20:12Z")
I’m on an e-mail list for church bass players; I and a number of my fellow listmembers are also on FaceBook. I’ve added several of these people to my Friends list. So many of the friend recommendations I get are other church bass players from the list who I hadn’t yet added to my list. I agree it’s a “friend of a friend” thing, plus “common interests”. So I’m friends with Person A, and he and I both list “bass guitar” in our interests. FB looks at Person A’s friend list and sees Person B who has also listed “bass guitar” as an interest, and decides I might like to meet/already know that person. Same deal with old schoolmates. ---
**Author:** ![MeanOldLady](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/meanoldlady/32/10737_2.png) [@MeanOldLady](https://boards.straightdope.com/u/MeanOldLady)\ **Post date:** [July 9, 2009, 6:39pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/15 "2009-07-09T18:39:39Z")
No, fuck that. Yesterday _they recommended my husband to me_. Now simmer down, folks, there’s more. Before anyone says, “Surely, you two have mutual friends,” and suggest that’s how they found him, I say No! Wrong! Not Facebookwise, at least. Riddle me this, Batman: He does not use FB, only signed up in 2005 because some girl told him to, she is and always has been his only FB friend. None of his friends are on my FB, none of her friends are on my FB, I am not friends with said girl (she hates me, actually), and as a matter of fact, 100% of the people on my FB are people I went to school with long before I knew my husband even existed (and only 1.5 of whom he knows quasi-personally), plus three friends that I know from work. There are no mutual friends among any of these people, in real life or otherwise. So what, praytell, is the haps? You know when he showed up as a suggestion? Do you want to know the exact date? Do ya?!!! Precisely one day after I sent a letter from my work e-mail to his personal account. $10 says that’s the e-mail he signed up with, and these bastards stole it! Am I paranoid? Not usually, but I am now… Oh, and another thing, I was reading boards here and the ad told me that I, by first name, have an IQ challenge. First, no I don’t, but who told you my first name? Wtf? ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [July 9, 2009, 6:59pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/16 "2009-07-09T18:59:36Z")
I was going to ask a similar thing. It is recommending as a friend somebody whose ONLY connection to me is that they also contribute to a website that I do a bit of (paid) writing for. This person lives on the other side of the world from me, we have no friends in common (the only person we would have in common is the guy who runs the blog, and I am not friends with him on Facebook). It’s kind of spooky, and not a little unnerving. The only thing I can think of is that this guy has replied to emails sent out by the website owner to all his contributors, and he has hit “reply all” on a couple of occasions. ---
**Author:** ![MeanOldLady](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/meanoldlady/32/10737_2.png) [@MeanOldLady](https://boards.straightdope.com/u/MeanOldLady)\ **Post date:** [July 9, 2009, 7:16pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/17 "2009-07-09T19:16:23Z")
When FB first started recommending friends to me (a highly annoying feature, in my opinion), their suggestions were almost always loose acquaintances. Fair enough, we probably have some friend overlap somewhere, no big deal, no fancy spy techniques are required to guess I may know those people. Then they started explaining why they made the suggestion, “So and so went to High School X,” or “Whatshisname went to X University,” etc, all fine. And then I saw the spouse, who has about zero internet presence, _the day after_ I sent an e-mail to his personal account (which I’ll guess he signed up with) instead of his e-mail address, with no explanation for why they suggested him… and then I thought, they monkeys be readin’ my e-mails! They should have put, “We’re guessing you two know each other because you sent six e-mails back and forth yesterday.” ---
**Author:** ![Swallowed\_My\_Cellphone](https://avatars.discourse-cdn.com/v4/letter/s/9d8465/32.png) [@Swallowed\_My\_Cellphone](https://boards.straightdope.com/u/Swallowed_My_Cellphone)\ **Post date:** [July 9, 2009, 8:05pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/18 "2009-07-09T20:05:03Z")
> [@otorophile](#): > > Seeing my high school teacher as a person I may know was fairly strange. I use an ad blocker, so I’m curious: are ads on facebook well tailored to what you write about yourself on your profile page? Absolutely! Before we were engaged, my now-fiancee started getting really pissed that all the ads were "Lose Weight Fatty!"and “Can’t Get You Man to Commit?” advertisements. When she switched her relationship status to “engaged” and tons more “diet, diet, diet!” ads. Most of which offended even me, and HEAPS of tacky wedding shit ads that offended both of us. Wedding this, wedding that! Buy a dress, get a ring, special make-up for your wedding day! Bullshit. She removed a ton of information, including her gender, from her profile page. Now she gets ads that are relevent to what is listed in her interests and that is based on keywords. I read an article about that recently too. Some woman got “lose weight to get your man to commit” ads when she was listed “in a relationship”, then the awful “lose weight for your wedding day” ads when she was listed as “engaged”, then all sorts of “pregnancy, baby, baby” ads once her status changed to “married”. ---
**Author:** ![CrimeThink](https://avatars.discourse-cdn.com/v4/letter/c/90db22/32.png) [@CrimeThink](https://boards.straightdope.com/u/CrimeThink)\ **Post date:** [July 9, 2009, 8:24pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/19 "2009-07-09T20:24:12Z")
Just a guess here but maybe it takes into account people who have viewed your site. For example a person views your site a few times out of curiosity because of some association and then Facebook recommends them as a friend to you. ---
**Author:** ![HorseloverFat](https://avatars.discourse-cdn.com/v4/letter/h/8e8cbc/32.png) [@HorseloverFat](https://boards.straightdope.com/u/HorseloverFat)\ **Post date:** [July 9, 2009, 8:26pm UTC](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462/20 "2009-07-09T20:26:26Z")
Your friends are probably doing this: [http://blogoscoped.com/archive/2009-06-12-n15.html](http://blogoscoped.com/archive/2009-06-12-n15.html) and importing your email address. On top of that it will do stuff like match high schools, interests, locales, etc. Its not reading your emails. Unless you give it your password it cant. If its using some API to read your email it would have been caught by now. Relax. Why would they need to steal your info when you readily gave it to them already? Age, gender, schools, address, email, etc. No need for your emails. [Next page](https://boards.straightdope.com/t/how-does-facebook-know-i-know-these-people/502462.md?page=2)