I had a look there. Besides from the fact that I got a chuckle from one of the previous questions - "Are there vegan clowns?" , it took about 1-2 minutes for my question to be answered. I had asked a question where my website is currently ranked #1 for and should have been the quickest answer. As expected, it was. Now, how did they find the answer? Did they google, msn or yahoo it - most probably (it was not a mainstream question). So a question remains as to why one would use them.
My guess it would be for a "human filtered" answer or for questions which someone cannot properly search for.
Now, I've been playing with Yahoo Answers a little - the answers there are answered in seconds in many instances. I tried to answer a question which had just popped up and 2 people had already answered it - all in the space of about 20 seconds. You could probably make a search engine similar to Jyve and just somehow post and grab answers from yahoo Answers (noting that you can also get Source results as well) and get similar if not better results. Just a thought.