"Adoptive/foster parents are not allowed to change their child's birth name so if they have a very unusual name, it would be horribly easy to track them down if you were so inclined."
Well, several of my children's friends are not registered on FB under their real names so having an unusual real name is irrelevant. Of course, if you know any of their friends' names you can hop through friend lists and find them if they have photos or other identifying info. However, for the vast majority of children, this isn't an issue is it?
WRT personal messages and online chat, no I can't supervise that. However, I know my children and I know everyone on their friend list and based on that I trust them. TBH, they barely use FB anyway. DS1 is now 13 and, obviously, once he went to secondary school I lost control of knowing who his friends are. I can tell he is fine though by watching his behaviour - there is no cyber bullying going on there for example. I can't control what they can't about online in the same way I can't control what they chat about at school. I can make sure that the parental controls are in place to avoid "accidental" discovery of porn and we have had The Chat about internet safety, what to do if they come across something inappropriate and that they and talk to me about anything - I won't be angry.
I have done my personal risk assessment and I am happy with how things are working. As DS1 gets older I will have a chat to him about how he should think about what he posts and how it will be there forever. His school had a huge lecture about FB postings a year back after a prospective parent printed out page of what she deemed "inappropriate" postings from pupils and sent it to the headmaster. He is therefore already aware that there can be consequences.
WRT alcohol, sex and driving cars, yes I would let my children do those things earlier if I was certain that it was safe, in a controlled environment and they were protected. In the case of cars, obviously this would be on private land and completely supervised! As children we all had a go at driving a car on private land before turning 17 and we also had a moped we used to ride round our garden (I must have been under 11 for that now I think of it).
Insofar as making tho children
about boundaries, I disagree. I think it has made mine realise that when I do say no, it is for a very good reason and I mean it. They know that if I think something OK then I will agree albeit with certain restrictions/conditions.
Everyone makes their own decisions for their own children. Whatever the given age limit on FB, if you do not deem it right for your child then don't let them have it.