I was confused for a second to see a "Page Not Found" error from Facebook. So note for others who get this and decide to ignore this post: "Page Not Found" apparently means "Please Log in"
With facebook doing this the volume of questions and answers will be great. I guess it comes down to how effectively they can separate good and bad questions and answers.
Most of the public stuff you read on facebook such as in groups is very low quality writing, they would have to have a really good filtering method for this to be usable.
It is obviously not possible to catch Wikipedia as a knowledge base, for the same reasons as it is impossible to catch Facebook as a social network or Apple as a content-distributing platform, and specialized collaborative sites, like Stackoverflow are years ahead.
