I had a facebook for years but I deleted it because some bad sh** went down and I got sick of everyone asking me about it. And it tore me to pieces to watch my classmates going on to brilliant careers and world travels and general happiness. And I had at least one stalker who wasn't a very nice guy.
I might make another one, though, especially now that it looks like the privacy settings options are better.
I read a lot of blogs and stuff, but I don't have an active online identity outside of here, okcupid, and gmail. Anyone here is welcome to say hi through those means, but they don't have the same friend-collecting mechanism as social networking sites.