I wonder how many parents of teenagers are in a panic right now?
The good ones aren't panicking at all, because they have the FB password as a condition of the child being able to use the computer or have a phone. True, a kid can update stuff from other people's houses, etc., but it would be a royal PITA. And yes, the kid could create a new account, but a savvy parent would catch that too by looking at the kid's friends' friend lists, which are unfortunately not lock-downable.
All it takes is paying attention, which many parents don't do these days.