We already have Microsoft Live QnA and Yahoo Answers. Amazon doesn"t believe that "three"s a crowd" and has released Askville.
The services comes with "virtual currency" called Quest Coins that is awarded for questions and quality answers (worth more than questions) but deducted for answers rated inadequate by others users. The currency can be redeemed at a forthcoming Amazon site dubbed Questville. Askville users are also encouraged to integrate external resources into their answers, especially Amazon products.