Answers.com have created an infographic for their blog illustrating the current fad for Q&A sites. Below are some of the answers they found on the current industry leading Q&A sites: Answers.com, Ask.com, Facebook Questions, Yahoo Answers and, of course, "the love it or you hate it" site of the moment, Quora.
You can download the full version here to post on your own blog.
Q&A sites have proven to be such a successful niche that Ask.com retired it's search engine to concentrate solely on this market. However, Q&A sites tend to be heavily scraped by 'made-for-adwords' (MFA) sites, which have given Google a lot of headaches recently, and also they are easy to exploit using sites like Mechanical Turk to hire people to ask and answer any old question. Do you think there is a risk they will become perceived as the new content farm?