Hitwise reports Yahoo! Answers has a market share of 96.10 percent in December 2006. Answerbag ranks second with 2.04 percent of the market and is followed by Windows Live QnA which serves 1.02 percent of the market.
Some other facts about Yahoo! Answers:
For the week ending 12/23/06, it ranked as the 100th most visited domain among the 500,000+ websites tracked by Hitwise. It ranked as the #2 site in the Education - Reference category, receiving about 1/5 of the share of visits to the #1 site, Wikipedia.
Slightly more than half (52%) of visitors to Yahoo! Answers were female for the four weeks ending 12/23/06. 22% were between 18 and 24, slightly less than Wikipedia's 27% of 18-24 year olds.
Yahoo! Answers received 53% of its traffic from search engines for the week ending 12/23/06. This was almost evenly split between Yahoo! Search, with 28% of upstream traffic, and Google, with 23% of upstream traffic. This means that Google is indexing Yahoo! Answers content, and is probably almost as effective at driving traffic as Yahoo! placement of Answers content on the bottom of the search page.