The stat in your subtitle misreperesents the actual finding. Media Metrix states that more than 50% of MySpace visitors are 35 years old or older. You forget to add the 11% of Myspace users 55+ years.

This misconception that social networking is for teens is precisely why you get so many creepy older people there - they want to be with the teens.

Ironically, now that we have stories coming out like this, the social respectability of these sites will increase and we might to see some normal adults. So the creepy adults are paving the way for broad general acceptance. Not to mention the kids who get started with social sites early and then just grow up with them.