I've been periodically posting about weird social coincidences, because I'm fascinated by them. Here are a couple more:
Via Zachary, I found this great group of people, mostly around my age, who have a Sunday night potluck circuit -- it's a great way to meet folks in the neighborhood who you might not otherwise get to know. At last night's event, I met a woman who looked familiar, and then I realized that it was because I met her in the hostel in Harper's Ferry, WV during my bike trip in the fall. She remembered, too, and we agreed it was a funny coincidence.
And from a few weeks ago: A few of us from my team at work took Metro to a meeting. After we sat down on the train, one of my colleagues recognized the person sitting across the aisle as an old acquaintance, and they struck up a conversation. Not very unusual on its own. But on the way back from the meeting, a different colleague sat in that same position in the car, and she recognized the person sitting in the same seat across the aisle as an old acquaintance. At the moment they started talking to each other, the person sitting to my colleague's side (not part of our group) recognized the person sitting next to my colleague's acquaintance, and they started up a conversation. She moved over next to him to talk after a moment, though, because she couldn't hear over the din of all the social serendipity...
As an added coincidence, all three people on my side of the car were women, and all three people on the other side of the car were men. I kept an eye out for other anomalies in the space/time continuum for the remainder of the afternoon, but none appeared.