Today I saw google adwords ad on YPN! It looks like they (Google) are trying to capture YPN's market... see image here: link
Both competitors advertising on each others contextual ads. Even though they do this, I don't see why it is a problem. After all Google is listed in Yahoo's main search results and Yahoo is listed in Google's main search results. So what's different about this apart from they have to pay.
I still think it's probably an affiliate. hey -- I always see Google Earth or Google Maps at the top when I search for MapPoint. MapPoint is the name of an MS mapping product. Years ago I predicted Google would do this, i.e. place ads for themselves as they roll out new products. Do you think they do any internal accouting for the clicks (the mapping group inside google pays for the click) or they just have someone in an office to say place this or that ad to promote Google properties?