Not a family member or close friend or anyone from this particular site. But one time a stranger came up to me in a supermarket who I’d been chatting to online on another chat/SPAM. He recognised me, but I didn’t recognise him, and it was a little awkward. The only other time something like that happened, I got a message on some site saying something along the lines of was that you I saw walking down such and such street today. That freaked me out a little.
But generally I have to say, our experiences online have been overwhelming positive.