Although I cannot answer that question, I have a suggestion for alleviating your concerns: Use a meta search engine, if you can spend the additional waiting time (for me usually 2-3 times the search time of a single search engine). In search for the former I have stumpled accross Jux2 that combines searches from Google, Yahoo and MSN. Unfortunately it does not (yet?) include Ask which I think is also quite a nice search engine. Moreover, it has a slick interface (although I hate their selection of colors).