Its good in terms of traffic of niche category towards our site/blog but not contributing towards pageranks. I thought google advice bloggers and website to do nofollow. Never thought its competitor also follow google's advice on nofollow.
The best place to put the link is the source box, but the link can be put in the body of the message . One should keep in mind that the link to the question answered should be relevant other it would be considered spamming and might get the account banned. Nowadays Yahoo Answers is considered a major source of driving traffic to the sites , affiliates also. Regards Tehmina
Links can be left either inside the answer's body or into the resource box, but be aware that spamming Yahoo Answers with whatever link will lead you to a ban since anyone can report you for not abiding by the terms. Of course you can leave your links, but they need to be relevant to the question. Just the other day I saw how someone was banned for being promoting a Taiwanese church as resource to Internet and Computing matters, which certainly is funny because I have never seen someone getting into MySpace or fixing a computer with prayings, LOL
I usually leave my link in the "whats your source box." Make sure you only leave your link on questions where your link is relevant. If you don't it will do more harm than good.
Leave the link if only your site is related to the question asked... otherwise, your account may get banned.