MySpace let these groups run wild and these are the two populations who dominate MySpace - youth (14-24) and 20/30-somethings who participate actively in cultural development (from performance artists to clubgoers to sex divas to wannabee celebrities). These sites are ideal for these populations, even if they make no sense to parents and professionals.
However, it does not address the way that MySpace has turned a whole generation of twenty-somethings into eight graders. What? He didn't put me in his top eight! OMG!