Yahoo! Answers just sort of snuck up on me. You can tell it is a real Web 2.0 service because it presents itself with three verbs: Ask, answer, discover.
Here is Danny Sullivan on its rise:
In May, Barry Schwartz wrote about Yahoo Answers hitting the 10 million answers posted mark, an impressive accomplishment particularly given the low interest and poor take-up answer search has traditionally had in the U.S. But some new stats add fuel to the idea Yahoo Answers isn't only bucking the trend but perhaps becoming a social interacting phenomenon like YouTube or MySpace.com. [Look Out Wikipedia, Here Comes Yahoo Answers! Part 1]He goes on to present the stats and to discuss its traffic relative to other reference sites on the web. He notes the very high volumes some 'answerers' achieve.
The model is an open one, where participants offer questions and answers and you can see why it seems to become addictive for some. The tone of the questions, and of the answers, varies a lot. A first impression is that participants roam over the serious and the frivolous: the service makes no distinction, it just acts as a platform to bring together questions and answers. It is about interaction, a form of connection. This is one way in which this - and some other significant web services, social bookmarking for example - differ from educational or other approaches.
Having spent some time exploring it, I am surprised that we have not had more discussion about it, particularly given the heat that Wikipedia discussion generates. Maybe I am just not looking in the right place .....