I am monitoring both google and yahoo for my search terms for past 6 months. Some of my conclusions would be that Google is changing their search results on almost daily basis, while I havent seen some major changes in Yahoo since ive started to follow search results. Yahoo is pretty big pain in the *** for me since there is no way, no matter what i do with my site (
SEO, updates, adding quality content, adding new pages), to get among first ten SERP, we are just plain stuck on #22. My vote goes to Google, not because of my positions, but because of constant improving and work. Yahoo is slooow with updates, and multiple listings just doesnt bother them. I have a competitor there which is on third AND fifth position. Another one is on second and 15th position. Such things doesnt happen in Google.