[amenhotep]

It's possible to mandate effective parental controls and then say "it's illegal to give your child access to facebook" and then just see what happens. You don't have to jump straight to making it technologically guaranteed by construction, maybe it's enough to just give parents the tools and an excuse to say no.

We don't need DNA testing locks on cans of beer that won't let you drink from them unless you're an adult, do we? It's perfectly possible for a parent to buy their child all the beer they want, and there's nothing stopping the children from trying to peer pressure them into it, and in many countries it's not even generally illegal to let your child drink beer! And yet almost all parents are able to almost completely enforce a reasonable level of restricted access, simply because society frowns upon it.