With the exception of Digg, all the major social networking sites had more women than men. I wonder why? Why do you think so? Personally, I know I have been on social networking sites since 1992 via Usenet and IRC. Yes, you might not have heard of these two, but this is way before Google came to the picture, kiddos.
http://www.informationisbeautiful.net/2009/who-rules-the-social-web/