Walt Mossberg:

Parents fret all the time about protecting their kids on Facebook, but many of the products and services I’ve seen that aim to help are intrusive, and inject the parents into the child’s normal, healthy online social life in a way that’s awkward for both.
You could co-manage your child’s account, or “friend” them on the service, which technically has a minimum age of 13. But those are time-consuming and embarrassing practices, especially when the offspring are teenagers, who generally crave some degree of privacy, even if they don’t merit full treatment as adults.
So I’ve been testing a service called ZoneAlarm SocialGuard that I think strikes a good balance between safety and privacy, between a parent’s peace of mind and a teen’s sense of freedom. Every five minutes, it monitors kids’ Facebook accounts for approaches by potential predators and strangers, cyber-bullying, age fraud, account hacking, and links to inappropriate or malicious websites. It uses algorithms that look for certain types of language, profile data, or other clues that unwanted activity may be under way.