T.N.
Ok, here's the way I see it.
Every child has to learn their way around (or not) many many different social situations. For example.
Knowing how to sit and listen in class is a social skill.
Knowing how to behave with peers during lunch at school is a different social situation.
Knowing what's acceptable behavior at HOME is yet ANOTHER different social situation.
As is church, dance, riding bikes with kids in the neighborhood, extended family dinners, grocer shopping....and so on.
Electronic social media is just ONE MORE THING ON THE LIST.
So, I think, if a child has not had many social issues in all those OTHER areas, it's not likely they'll have issues with social media either. That is to say, if the child has self respect, common sense, and good modeling with regards to social media, it should be fine.
But as with every other social situation, there may be bumps in the road and learning opportunities and I DO believe when it's NEW to a child it should be monitored closely (as closely as a parent might monitor any other social situation when it's new to the child). So how you monitor is up to you, of course, based on what you already know about your child's social tendencies.
Anyway, my kids are 20, 18, and 15, and everything I know about social media has come from THEM, sigh, not the other way around.
So at first it was kind of a "you have been smart and trustworthy and made good decisions in every other way, so you can HAVE this. However because I need you to be safe and KEEP making smart choices, I'll be keeping a close eye on it for awhile". I mean not word for word, but that was the general feeling we had about it at first. I haven't had a single problem with any of them.
And yes, I, too, wish they could stay little forever!
(Ok maybe not forEVER but a little more time then you get!)
HTH!
:)