When you reach Level 2 in Yahoo Answers you earn the ability to post URLs in your answers. These backlinks are nofollow but with Yahoo Answers being such a huge support forum, it is easy to accumulate lots of relevant, quality nofollow backlinks. Is there a good benefit to having these backlinks or will Google consider a certain amount of them spam and penalize one instead?
It doesn't mean that they are nofollow that they are useless! Yahoo Backlinks can help you get even a much better rankings... Just be sure to post your link ONCE per 50+ answers given and do NOT spam... Only on related answers!!!
Even if you do provide good value in your answers yahoo will find out and ban your account. You will get traffic but in the long run you will get banned..