Parental Control - How Far Do You Go?

[Jimbo]

Maybe someone could give me a little advice. By accident last night I found out my 15 year old and her friends and others I don't even know (nor does she I found out) have created webpages of sorts for themselves on some common website, many posting pictures and personal information of themselves. Apparently, their individual pages are accessible for posting messages by others if they get permission. Somehow she had stuff from guys she didn't even know I felt some of the other kids' pictures, as well as the quasi-porn some posted, the absolute worst language they used, and some with sexual or quite violent descriptions of things they wanted to do was totally inappropriate and she (all of them) were setting themselves up for trouble, be it perverts, conartists, whoever. She shut down on me and told my wife alot of it was just people venting or feeling their way in the world and it was harmless. I told her shut it down, delete it do whatever you have to so it doesn't exist on your PC anymore.
Just a sanity check. Am I over reacting? Or does this sound like the kind of thing parents are supposed to do given the internet freaks we hear lurking for this stuff, as well as her (former) friends with serious mental issues. Are these sites harmless? Sorry I can't remember the url here at work.