My son has an iPhone 3GS. He is 11 years old and absolutely loves it. His aunt gave it to him when she upgraded to an iPhone 4S.
He wants a Facebook account which I have said no to. Besides the fact that is too young, I just won't let him on such a forum because it has been embedded in my mind that bad things can happen on social networks to the young. Trolls, bullies and who knows who else are only too ready to make someone else's life a misery and so the answer remains a no for the forseeable future.
I was surprised to see that most of his friends are on Facebook even though they are below the consenting age for the network. Perhaps even more surprising is that I have no problem with his playing 15 rated games on his Xbox and watching 15 films if they are not too violent or graphic. He is mature for his age ane very sensible so I am happy for him to make choices in such matters. However, on Facebook choice often goes out of the window and I can't get my head away from the risks that it offers.
I admit that I personally hate Facebook because the content is often trivial, the design is terrible and it doesn't seem to have any redeeming features. 700 million people can't be wrong I suppose, but I still hate it and my son won't be setting up an account any time soon.