As the parent of a teen, I'm concerned about those types of sites as well. It's just a downright, dirty shame that some perverted jerks are determined to suck the joy out of what should be a fun place for teens and young adults
.
My son hasn't expressed a desire to open a myspace account, but he does frequent many different areas on the web (mostly pertaining to gaming). He's very aware of what he should and should not be entering, information-wise.
As parents, it's our duty to remind our kids and their friends that revealing too much info is dangerous. Sad, but true.
So, just watch out, folks. Enjoy the sites, but don't give out personal info that can, in any way, be tracked back to you IRL.