“Google is a company fueled by innovation, which to us means trying lots of new things all the time — and sometimes it means reconsidering our goals for a product. Later this week, we will stop accepting new questions in Google Answers, the very first project we worked on here.”
There’s also a brief article at Forbes.com.
I never used Google Answers, and only ventured on to Yahoo! Answers once or twice. But to me Yahoo! Answers appeared to be a (a) more accessable and (b) usable product, even if a lot of the answers were less authoritative than some of those being produced on Google Answers.
Pages from Yahoo! Answers definitely appeared in a lot of my search results when I was surfing the web for various things, which would have contributed a lot to its success at the expense of Google Answers, which was a fairly buried product as far as discovery of it was concerned.
Looking at the success of Wikipedia, not many people who are using the web are overly concerned about transparently well researched and authoritative information on the web. They are more than happy to take the quick and dirty. Another area where Yahoo! Answers was ahead of Google Answers.