What are the best question-and-answer services online, apart from Yahoo Answers?

Why do question-and-answer services such as Yahoo! Answers and Quora have a points system, and so-and-so like that?

• Answer:

  So people can be encouraged to answer. Correctly or at least related to the question for that matter. It's kind of a reward system, you may answer but what would you gain from it? Quora's more lax and very generous with their point system wherein you gain credits with every upvote of your answer or when someone follows your question, even giving away freebie credits from time to time etc. Doesn't matter if you ran out if credits or not, you can still use basic features like asking and answering a question. Not much with Yahoo! Answers though, IIRC points will be deducted from you when you ask a question, if you ran out if points you won't be able to ask a question anymore. You can gain more points when you answer a question, there's a loophole in that system though, it doesn't matter if you answer correctly, so you can still gain points, I've seen many users take advantage of this hence the many nonsensical answers in YA. Sometimes people are discouraged from answering since someone already got the best answer award. So discussions in YA end rather quickly. Unlike with Quora that upvotes answers, which shows some of the best answers rather than picking just one among the rest.