Sample coverage which points to a WSJ article on the subject and explains some of the legal environment in the United States.
http://www.pcworld.com/article/256740/facebook_ready_to_officially_allow_children_under_13.html
I can find no indication that anything further has happened. Anyone got anything? I did not notice this at the time (or have forgotten), and in general, I don't care, but I just learned that there's an enormous reservoir of I Hate Zuckerberg and/or FB and/or kids-being-online out there and then further learned that there's a bit of an exception if there was a carefully created, managed and monitored kid-focused FB or similar. Which means the product opportunity is real, and I'm wondering if it's ever going to happen, or Our Litigious United States ensures it will not.
This HuffPo coverage from last September has some claims in it about how many under 13 year olds are already on FB:
http://www.huffingtonpost.com/2012/09/19/under-13-year-olds-on-facebook_n_1898560.html
However, given that one of their arguments is that FB advertises sugary foods, I'm not sure I find that particularly compelling. Sugary foods continue to have a lot of advertising space in other places kids are allowed.