Ooookkkaaaay. This is actually interesting. Yahoo's new "Mindset" search allows you to weight search results based on how "commercial" they are. I tested this by searching on product with the slider set to "non-commercial". Instead of Google's 50 pages of ads I got a very useful review in the 3rd hit.
Of all the search experiments I've seen in the past year this one has impressed me the most. In the search wars, filtering out 'commercial' sites is a dramatic and risky move.