Shawn at DigitalPoint forums started a thread named ctxt_ad_keywords where he explains a possible method to influence the relevancy of the Yahoo Publisher Ads shown. Shawn says, at "first glance it looks like someone can pass a ctxt_ad_keywords variable to the script to maybe get ads based on keywords." He explained that he tried it and it returned an error, which leads him to believe it must be turned on, on a per account basis (much like how Google AdSense does it).
More information and forum discussion at DigitalPoint Forums.
