Seems to be a discussion going around and around in circles. If adults on this very thread have said, they have encountered difficult/dangerous/unwanted situations with Face book, then it is obvious minors will do the same. Rather than turning to the Nanny state, perhaps it is time for parents to take the reins (again) and use a decent parental lock or block for pages that are eighteen plus, or settings, that they do not want there children accessing, with out there knowledge. Yes those of you who sceam, children have rights, they do, and a parent has responsibility to keep said child (a) alive and (b) out of harms way.
So thus take control of the situation, not relying on the state, school, courts to do the parenting, for them.