Interesting post Look Out Wikipedia, Here Comes Yahoo Answers! which includes the following passage:

“Aside from traffic, I think the more interesting comparison between Yahoo Answers and Wikipedia is the different approaches. Wikipedia aims to have everyone comprehensively build a corpus of knowledge in an organized fashion. Yes, disorganized in the sense that anyone can change things. But organized in that each topic gets a single page containing the contributions.

Yahoo Answers deals with one-off question answering. There’s a corpus of knowledge growing there, one that’s even organized into categories, but all the answers on a particular topic aren’t neatly put on the same page.

That’s not necessarily a disadvantage. In fact, it may be part of the reason Yahoo Answers is pulling in an audience that might never want to contribute to Wikipedia. Wikipedia, if it were a computer game, would be a strategy game where you take a long view to win a campaign or goal. Yahoo Answers is a first-person shoot-em-up. Questions appear, and as soon as one is shot down with an answer, it’s on to the next one.”

With the ATTRACT website hosting 2200 questions and the NLH Q&A site hosting 3100 that’s a total of around 5,300 questions and answers. Small compared with the 10 million on Yahoo answers. But these are 5,300 ‘good’ answers. The number of repeats questions is rising (probably around 5-6% compared with 2-3% when it was just ATTRACT). What happens when we get to 10,000 answers, 25,000 answers? Will we have answered 50% of likely clinical questions? Will we then have a more useful resource than, say, eMedicine and Uptodate?