Honestly, I would suggest you get a Facebook account and start playing around with it. The answer to all your questions are "it depends". In part it depends on

Honestly, I would suggest you get a Facebook account and start playing around with it. The answer to all your questions are "it depends". In part it depends on how Facebook evolves over time, in part it depends on how much they want to curate their content, in part it depends on what their friends do with the content your children are incidentally a part of. More than any of these, however, it will depend on how well they understand the implications of their actions online. You're going to be in a much better position to communicate about these implications if you understand exactly how they're interacting with their online identity. This means having at least a reasonable understanding of how interacting on Facebook works and, like it or not, Facebook is complicated enough that the only way to understand it is going to be using it.