"What we’re seeing is a modern incarnation of white flight...It should scare the hell out of us." -danah boyd-
danah boyd, a fellow at Harvard's Berkman Center for Internet & Society, has spent the past four years studying, observing and analyzing how US teens use social networks. What she's found is that high-school students began showing a trend of white, upper-class and college-bound teens migrating to Facebook while less-educated and non-white teens were on MySpace.
Research by the Pew Internet & American Life Project further elucidates the social network stratification. Their December 2008 study showed that, overall, Facebook users are more likely to be male and have completed college, while MySpace users are somewhat more likely to be female, black or Hispanic, and to have not completed college.
Read more stats in this New York Times blog post on the topic. Or check out boyd's blog and her essay on the topic, which she presented at the Personal Democracy Forum.