I am wondering if it’s ever happened that dopers have interacted on the SDMB, then interacted in real life, not realizing that they were both dopers who had interacted on the SDMB before.
Of course this may well have happened without anyone ever realizing it, but are there cases where the two (or more) dopers involved came to realize what had happened?
-FrL-
Yes. Here’s a thread where a couple of people talk about it happening to them.
http://boards.straightdope.com/sdmb/showthread.php?p=7599128
I’ve met a couple of people I didn’t know were lurkers until later, though I haven’t met any actual members accidentally. (Of course I would only ever associate with Charter Members- the ‘new’ families are just a bit gauche for my set.)
Other than the people I’ve introduced to the Dope, there’s been one person I’ve met online in a writers’ group.
His sig line from here matched up to his sig line there, so I asked him.
And he disappeared. 
Life is short…
When I was teaching at a small liberal arts college I had a kid sit infront of me one day with a SDMB shirt on. It secretly bothered me all semester that he was a poster and I had no idea who he was. Cognizant of my anonymity I stayed quiet and still to this day do not know who he was… 
This was a while ago.
Ran into Samclem one time at a certain business located in his municipality of residence. That was some time after first meeting him at a Dopefest.
Didn’t realize it was him 'til I was back in the car and headed home…
Well, there’s Qadgop and Elfbabe…
I started talking about a message board at a party last year, and as usual, no one knew of Straight Dope, until I realized I was talking to a Doper, who turned out to be Moe.
I ran into ElvisL!ves at the National Park near my home, but we’d already met in real life.
Not too surprising. We live in the same town.
I knew onetime poster KevinLeeC before either of us joined the Board. We’d both been Straight Dope fans before the Board existed.
I met a Doper at a conference once, but he claims to lurk more than he posts. Never did tell me his username though…
I’ve moved this to MPSIMS because that’s usually where these kinds of threads go. I think we actually had a thread about these kinds of encounters recently, too.
I know of one Doper to whom this happened - and it’s kind of funny, because she in turn is an IRL friend of mine who I accidentally discovered was a Doper.
A couple of jobs ago I worked with an intern two cubes away who turned out to be a Doper. She wasn’t a member for very long, though.
I met Gundy (who hasn’t been on the Dope since about '05) at a temp assignment. I was sitting at my computer, pretending to do some work, when I overheard my cubicle neighbor (loudly) explaining to someone on the phone that she was arranging something akin to a fest for nerds. Can she be talking about the DopeFest? So after she gets off the phone, I lean over the cubicle–not having ever spoken with her before–excuse myself for overhearing her conversation, and ask if she was by any chance talking about a Dope Fest. There’s an uncomfortable pause, accompanied by a blank look. Oh my God, she has absolutely no clue what the hell I’m talking about. She probably thinks I’m some sort of druggie. “Oh my God! What’s your screen name?” she asks. Phew.
How about one degree of separation?
One time Oy! posted a request for help translating a thank-you note into Portuguese for her Brazilian cleaning lady. I took a first pass at it and had my wife to the official polishing and posted the response. The lady’s name was familiar and unusual, and the OP location was Trenton, so… a few posts later we found out that we share the same cleaning lady. That was kind of neat :).
About the closest I can come is discovering that anu-la1979 and I work about two blocks from each other and were often on the subway at the same time. It’s possible we’d seen each other before, but we hadn’t interacted.
I’d be willing to bet we aren’t the only two Dopers working in downtown LA, but I can’t prove that, obviously.
I’ve got a profile at OKCupid, and have ended up being IM pals with a few people from there – one of whom used to post here as audient (and who intends to return as soon as we go back to a free board). Do IM pals count as IRL?
I’ve never met any Dopers, but I’d love to! Sadly, I don’t live near enough to anyone who likes me. 
That last statement strikes me as being HIGHLY unlikely.
I know there was a thread a while back about developing a proper secret Doper hand signal, but I think we need to be less subtle than that. We need to develop a cool SDMB clothing line so we never miss each other! Maybe a t-shirt that just says, “Hi, Opal!” or something that would be obscure enough to keep the general public at-bay, but completely obvious to those for whom the message is intended.
No, really. Awhile back, there was a thread for a central Ohio Dopefest. I was going to attend, but it was shortly after my MegaPitting, so I posted and asked if anyone wanted me there. Nobody said a word. So while I know there are quite a few Dopers who think I’m okay, they all live far away. (Hmmm, mebbe there’s a correlation there…?)