Yahoo Answers recently added a feature--similar in appearance to Google's Gmail stars--that allows you to "star" individual answers. Those starred answers are then added to your public profile page, and you can view what other members have starred that answer. Most importantly:
"Starring questions lets the Answers community surface the best questions on the site. When a question is starred, it is automatically nominated to appear in the new “Popular” list on the front page of Answers (check it out!)."
Yahoo Answers community members who responded to the blog entry notifying them of the change said the feature is welcome, but a complementary option to "downgrade" an answer would be useful as well.
Yahoo Answers used to offer a "thumbs up or down" option, but that feature was removed after members complained there was no way to police malicious "thumbs down" attacks on user answers.
I'm not much of an Answers user, but I can see the star feature working well for the service. By allowing users to explicitly annotate good answers, Yahoo is providing a tool that strengthens social connections. The absence of a negative rating tool forces the community to either ignore the worst posts--in which case they should fall in popularity--and/or comment on the answer, which increases the site's page views.
The only problem I see so far is that Yahoo hasn't updated its FAQ. The FAQ still lists information for thumbs up and down but no information for stars. Bad project management, bad!
One other thing--the Answers stars are similar to Flickr's interestingness and the del.icio.us hotlist. I would really like Yahoo to release a Yahoo zeitgeist site that collates the most popular answers/photos/links from each of these sites.