Search Engine Watch blog has a good post about how Yahoo will no longer be allowing companies to purchase ads linked to the trademarks of their competitors. From what’s being sent to Yahoo search marketing advertisers:
On March 1, 2006, Yahoo! Search Marketing will modify its editorial guidelines regarding the use of keywords containing trademarks. Previously, we allowed competitive advertising by allowing advertisers to bid on third-party trademarks if those advertisers offered detailed comparative information about the trademark owner’s products or services in comparison to the competitive products and services that were offered or promoted on the advertiser’s site.
In order to more easily deliver quality user experiences when users search on terms that are trademarks, Yahoo! Search Marketing has determined that we will no longer allow bidding on keywords containing competitor trademarks.