Yahoo, which apparently began selling ads for sponsored search results without labeling them as such, has changed its policy regarding these sponsored ad sections. Ads that were clearly sponsored displayed at the top of search results, with a company logo, and were not included in the organic search results.
While Yahoo did not acknowledge this outright, it was rather clear that these sponsored ads were not labeled, which means that the end user could easily mistake the sponsored ads for the number one search result. This occurred specifically with a Special K search. You know, the cereal. This initially occurred over the summer, and linked to a third party website that offered Internet marketing and search services. A mini uproar took place, and now Yahoo has indicated which ads are sponsored with a link below the search result, which directs you to the associated "About" page.
Still fishy, but a band-aid fix nonetheless.
With Yahoo going through so many major changes this year (some rumored, some having already taken place), specifically on the advertising and search end, I imagine that questionable behavior would not be taken lightly. Microsoft has been tweaking its ad and search sectors as well.