Facebook Application designed to work similar to yahoo answers and a bit of tweaks.
You would want to look at some additional projects - -
Facebook Application Show
Fascination at Peak(Facebook Application)
Yahoo answers is a part of yahoo.
Here questions can be asked by people after they have created their accounts on yahoo.
They get 2 points for answering a question
yahoo deducts 5 points for answering a question.
10 extra points if your answer is chosen as the best one.