If you are referring to traffic to your site via Yahoo Answers, then my answer is both yes and no. I think it depends greatly on your topic - for a highly competetive niche, your answers may be "flagged as spam" by your competetors - for spite (beleive it or not, it does happen and Yahoo may eventually disable your ability to respond to questions). You may initially receive an increase in traffic, but a lot of said traffic may be curiosity. I don't think much traffic from Yahoo Answers convert to sales. I have noticed, however, that while searching on various topics some of the top ranked results have been Yahoo Answers, although rather old questions/answers.