A member asks how long it takes for sites to start being indexed in Yahoo. Apparently, not long, if you utilize this practice. That's not to say that you should spam your site URL throughout Yahoo! Answers, but if your website is related to a question being asked and can help someone find the answers, then it may be useful.
A much older WebmasterWorld thread says that without this practice of linking in Yahoo! Answers, you can simply wait the standard time of 6 months to one year to be indexed.