I have heard about 3-4 of them and haven't used any. Since many of them seem to be social networking sites, I would like to point out that Orkut was and still

I have heard about 3-4 of them and haven't used any. Since many of them seem to be social networking sites, I would like to point out that Orkut was and still is the biggest "web 2.0"/social networking site. It'll be interesting to stack them up against Orkut for market share.