Google cannot escape their fundamental conflict of interest: they make money by selling web traffic to advertisers, then buying that traffic back at discounted rates and re-selling it again, over and over. None of their revenue comes directly from search, though search is their primary source of raw traffic. Their search results don't have to be good, they just have to be good enough to sustain traffic. And right now there are so many people who reflexively use Google out of habit that their results could deteriorate substantially (and many would argue already have) before it impacts their shell-game revenue stream.