This is a rather interesting article on why Yahoo should surrender and use Google advertising, in much the same way as a number of other smaller search engines have. It mentions that as a result, Yahoo could increase their average search revenue from $0.10 to $0.17 adding US$1.5 billion to their bottom line. I cant see this ever happening in the immediate feature, I think we are still in the early stages where each major player Google, Yahoo and MSN will continue to do battle for market supremacy. I would also not like to see this ever happen from a webmaster point of view, as the Yahoo Publisher Network is a viable alternative to Google adsense and serves to keep Adsense competitive and maintaining a decent revenue share split with their publishers. Currently the revenue share percentage is not openly disclosed and is just the subject of speculation.