Now the real question is coming as "Should Facebook, even with some sort of "Child-friendly filter", be accessible to children" ?
IMHO, the answer is a red and clear NO, especially since Internet can really easily be a wild place in which any not-prepared person can easily get lost and make bad encounters.
It's a place accessible to everyone but the risks are often overlooked and the slightest bit of maturity would be expected from someone to use a computer, let alone access Internet.
I don't think it's a bad thing by itself if children have access to the main communaction platforms to chat with their friends and communicate with their parents. However, I agree, parents should be prepared when they let their children to use the web.