Ah yes. COunt me in as being a magnet for people like this too!
Although in my two instances, it was friends who overshared in my presence. Once, many moons ago, a friend and I were doing weight watchers together. And as everyone does, we were chit chatting with the others as we were waiting for weigh-in. Now while its fine to say "oh i'm nervous, i didn't stick to the plan too well" and stuff like that, my friend is the queen of oversharing. She launches into a diatribe about how she KNOWS she gained since mother nature had arrived, and so on. The poor woman next to us had the deer in headlights look!
And this same friend, another time, when we were all hanging out at another friends, overshared about her HUSBAND. Several of us were jokingly taking about scrabble, but nothing personal, just generally, and having fun. She comes up and proceeds to tell us what postitions they prefer, and why, and also discussed ahem, size. mind you, her DH was in the other room! we all cringed and told her to quit it.
And then there's my manager at work. Who is divorced, has a rat for an ex-DH, money problems, etc etc etc. She goes on and on to anyone and everyone about how terrible thing are for her. Looking for sympathy, I supposed but really its gotten old. Although she was told by our DM no more, so its stopped, thankflully, for hte most part.