I've already written about this problem of "girl fight" videos on YouTube. See here and here. With the recent felony case of 8 high school girls and guys beating up another girl in Florida, it finally is getting attention in the national press. This NBC segment is quite good, given the constraints of national news on TV.
It's interesting that the judge in the case forbid the high school students who engaged in the beating from going on MySpace or YouTube, or it sounds like the Internet in general. YouTube's user policy states "Graphic or gratuitous violence is not allowed. If your video shows someone getting hurt, attacked, or humiliated, don't post it." But it appears to be pretty easy to find videos of girls fighting and also guys. Here's one that has been up since December 2007 and has over 160,000 views.
WARNING: Graphic violence and language. Viewer discretion.