Social networks confront challenges in rush to attract youngest users

A growing crop of social networks are racing to capture the loyalties of the Web’s youngest and most vulnerable users.

The rush to capture young users has sparked fresh concerns from lawmakers and health advocates over whether social networks will keep children in front of computer and mobile-gadget screens for too long. They also worry about online predators. Networks that specialize in kids tout themselves as safe environments for children, although they acknowledge that there may be no fool-proof way to block predators. Yoursphere, for instance, says it does a thorough background check on adults who register their children for the site. Under law, the sites must seek permission from parents to sign up users younger than 13. Facebook restricts users under that age, but an estimated 6 million underage users have lied about their age to get on the site, consumer groups say.