Yahoo Answers allowed registered users to post links as answers but since yesterday, those links have not been clickable. Webmasters at both DigitalPoint Forums and WebmasterWorld have been complaining about the issue since 4am (EST) yesterday. But it appears that this is just a technical bug.
Yahoo! Answers link update from the Yahoo Answers Blog said they "are working to fix the problem and we don’t yet have an estimate on when it will be done. Sorry for the inconvenience - we will keep you posted."
But why the sudden change?
Will Yahoo be slapping on nofollow attributes on those links? I don't believe they have had nofollows before this update (I can be wrong). Anyway, time will tell.