http://www.theregister.co.uk/2006/05/02/amazon_ditches_google_microsoft/
http://a9.com/amazon
I'm not sure how financially driven this decision was, but my (very) unscientific testing a few months ago put Google behine Yahoo and Live
http://www.noelwatson.com/blog/PermaLink,guid,e038a044-fe1d-4275-860d-f60bf549954a.aspx