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.<p>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.