Technically a general chat board, but frankly no one ever visits it and I don't expect anyone to ever visit it. But it's also my fault, I really don't put much time into it. It's really more for coding practice and not much more.
Depends, but a lot of people probably try to present themselves in a certain way to their 'friends' on Facebook. Generally that can hamper discussion because people may not want to argue or get overly into a point. Equally people may not want to discuss or join pages on Facebook that take stances on issues such as religion, politics and other emotive issues. And people tend to be more confident in their discussions if they feel anonymous.
That's obviously not the case for a lot of people, but a fair chunk of people on Facebook use it strictly for keeping up to date, rather than actively discussing things etc.