According to new Hitwise data released today, Facebook has experienced tremendous U.S. based growth over the past year. It’s not surprising, but it has come at the expense of the previous leader of U.S. social networking, MySpace, who’s traffic is down over 50 percent over the past year. Also experiencing tremendous growth is Twitter, who has grown by 1,170 percent over the past 12 months.

Another metric where Facebook is dominating the competition is in time spent on the site. Facebook to over 23 minutes per user, per month on the site. Contrast that with Twitter where traffic to the site has dropped by 56 percent. The reason for Twitter traffic dropping is most likely due to the surge in desktop applications that provide alternative interfaces for monitoring Twitter content.

Hitwise also provided demographic data for the top U.S. social networks which illustrated tremendous growth among older demographics for Facebook. No matter what chart you look at however, MySpace is loosing significant market share to Facebook, a story which has played out quickly over the past couple years. The result is the “AOLization” of MySpace.

Regardless of this trend, it’s clear that Facebook continues to experience tremendous domestic growth, and it’s expected to continue over the coming months.