Meet Rich. He's 37, loves photography--and has a penchant for the under-21 set. As for his favorite films, Rich writes, "Give me a movie with boys in it, I love it." He brags of his sexual prowess with boys.

Given his lurid obsessions, you'd think Rich would want to hide, but his profile at social networking site MySpace.com includes not only information about himself but also an E-mail address for future correspondence.

Tech-savvy teens don't always play it safe online. Photo by Sacha Lecca

Most of the 305 contacts listed on Rich's MySpace page claim to be kids--"claim" because the identities of strangers in cyberspace are hard to verify. In their own MySpace profiles, several of the kids responding to Rich are posing in their underwear; one says he's an 11-year-old who sneaked by MySpace's age controls by claiming to be 18.

MySpace and social networking sites like it offer thriving communities where young people engage in countless hours of banal chatter and photo sharing. Not coincidentally, social sites also have become hangouts for child predators, child pornographers, and other lowlifes.

It's a high-risk dynamic with potentially terrible consequences. In February, the naked, strangled body of 14-year-old Judy Cajuste was found in a New Jersey trash bin, and the body of 15-year-old Kayla Reed was discovered in a California canal. In both cases, investigators are probing possible connections to MySpace: Cajuste had told friends of meeting a 20-something man there, and Reed logged into her MySpace account the day before she disappeared. There are dozens of other examples of young people lured into "friendships" that put them in danger.

Several teens we talked to acknowledged their peers could be susceptible to come-ons from strangers. "It happens," says a 16-year-old girl. "You're a young girl, and people compliment you. You're more willing to meet them."

MySpace, in an effort to better protect its millions of young members, just hired its first chief security officer. Hemanshu Nigam, who starts this week, played a central role in online safety at Microsoft until being hired by MySpace. Before that, he chased down child predators as a U.S. prosecutor.