Don't believe what you read about MySpace's demographics. Recently comScore claimed that 40%+ of MySpace was in the 35-49 age group.
How to assess? One way would be to randomly sample MySpace profiles, looking for the self-reported age, and they assigning some probability that the age was accurate.
A sample of profiles found by this Yahoo query found:
The youngest age listed was 16.
Doing a much larger truly random sample would be a fairly accurate way to find the self-reported ages of MySpace users. Moreover, many of the self-reported ages are clearly wrong. (Do you think there are any 13 year olds using MySpace? They'd have to lie about their age to get past the registration.)
It's very likely, however, that 40% of the users are NOT 35-49. And that's just counting profiles. Actual usage is gonna be dominated by the people with free time.
The upshot: Demograpic tracking on the internet still sucks.