I looked on Wikipedia and there’s about 200 sites listed, give or take.
I’ve never heard of most of them. I’m familiar with Facebook, Livejournal, Myspace, Twitter, Xanga, Tumblr (duh), DeviantART, MOG, Imeem, and Friendster.
I’ve never heard of Kiwibox. It is “a social networking destination and online magazine for teens, with over 2 million members, Kiwibox is a social network with user profile pages, widget support, games, magazine and a TV section.”
I tried getting into MySpace because my co-worker asked if I had one, but I tired of it after a while. I only got into Facebook recently to keep in touch with my friend who’s studying in Japan, but now that I use Skype and MSN, I don’t use it as much.
There was an incident where I thought I was being subtle and posted some less than savory information about a person on MySpace; needless to say I stopped talking to that person, more out of guilt than anything else.