Yahoo Answers?
Yahoo! Answers is a site where you can ask questions on any subject you wish. You can also serve as an expert and answer other people's questions. Or browse the already answered questions.
Is it me or is this what libraries already do and do well? We take questions and answer them using quality resources. This brings up the same issues as Wikipedia where the answers given may not be correct and it is up to the community to judge the correctness of the answers. Another site where a large grain of salt must be poised and ready to use.