Looks like I have 146. Many are guitar-related - Dopers pinging me behind the scenes to ask a question about buying a guitar or music in general. Hmm - hadn’t realized it had happened a bit.
Many of us have hung around here for 15+ years, but really use the SDMB for what it is: a great way to dip into conversations about interesting stuff.
Spontaneous, non-begged-for PM - maybe a dozen. I can’t know for sure because there have been times when I’ve messaged back-and-forth with individuals and we’ve had long exchanges. Every once in a while, I just do a mass purge.
But it’s very rare for anyone to ping me with “about what you said…” and equally rare for me to do the same. Unless it’s too private and personal, I just dump it on the boards.
I’ve had about six PMs since I joined in 2008. And four or so of them were people asking me how to do an illegal thing which I mentioned doing in a thread. 
Since 2011, I have accumulated 67 messages. A couple of moderate warnings are included in this.
Since 2003 I’ve received 81 and sent 77.
Most are one-offs initiated by others with a single reply from me. The topic has always been related to some thread that person & I have both posted to. Occasionally it goes back and forth twice. Very occasionally I’ll make the first PM and get the one reply.
So overall that’s about 1 short exchange per 2 months. Or one per 150 posts.
So far there are two posters with whom I’ve exchanged off-board contact info. We very occasionally email one another items of mutual interest we find out in the non-SDMB world. (Yes, Virginia, it really does exist :))
OK, inbox only = 166.
Still has me wondering why.
No idea, as I delete them, but it can’t be very many other than from the time I offered free genealogy searches.
7 in 14 years. I need to get out more.
8 years, 4 messages. I’m not one of the cool kids.
One. Requesting a photo for the SDMB scrapbook. Of course, I’m more of a lurker than a poster.
How often are you contacted through this message board?
Frequently.
My private message box has 486 messages (97% full).
I’m always having to go through to cull old messages to make room.
Because we like you, DAMMIT! 
Dude! I think I got a PM from you once!? You’re in western PA, right?
No kidding!
Twenty-five in the last one-and-a-half years. (I can’t be bothered to check my archives from before then.) Though only one is actually just someone just wanting to talk to me, and not a private comment about something I said in a thread.
I get thanked for defending people or calling someone out sometimes. I occasionally get someone who is worried I might say something I shouldn’t. And then there was all the Bible thread stuff.
I’ve received 56 PMs since I’ve been here. The overwhelming majority are about games that I’ve played. Now I need to get chrisk to start up another game of haggle.
None that I’m aware of and hope there never is. PM’s are usually not the most insightful of discussions. Either they want something from me or want to say something hateful thinking I’ll actually give a crap what they have to say. But I’m always amused by drama queens so I guess it would add to the entertainment here.
How do you know this is what people want to communicate to you if you’ve never received any PMs (that you are aware of)?
Right now I have 87, but I’ve had to empty it out several times for space.
In the last year, that’s been inflated by Skald letting me know when he’s started a new hypothetical.
Most of them are health questions, polyamory questions, and a few "how YOU doin’? 
" kinds of things. A few from a while back when I snapped at another poster and got my one and only Warning (on purpose; it was worth it) asking why I did it or why I didn’t just Pit him instead. I do get some, “I’m so glad you said X in that Y thread, because I was thinking it, but I couldn’t say it!” - those kinds of PMs that trolls always claim they’ve gotten bucketloads of. Also some, “I’ve always wondered about N, but didn’t dare ask!” Those PMs are why I often post to threads even when obvious troll is being obvious, because I realize that other people are reading and getting value out of it sometimes, even if the OP is a lost cause.
I’ve sent a couple of unsolicited PMs as well, but mostly I don’t, because I’m afraid it might come across as presumptuous or invasive.
I have never sent, and never received a “hateful” PM.
That’s what The Pit is for.