For the life of me I can't actually find a flaw with this idea. Google does track you, across the entire internet, and it does know what its shown you in the past. It can cross reference your multiple accounts, and the Google corporation undoubtedly buys whatever data about you that it can't directly access through FB, and other sites.
The more I think of it, the more arguments I can find for this assertion than with problems with it. It was either Sergey Brin, or Larry Page that openly admitted years ago that in any non-consumer paid-for service, like a search engine, the results will eventually be gamed in favor of the sponsors. If Google sells our data to whoever wants it, we might only see whatever a sponsor wants us to see. Maybe you would like radical Islamists to be corralled to more moderate websites, but this could as easily redirect regular people into increasingly moderate viewpoints or perhaps even increasingly extremist viewpoints. It could stifle unpopular opinions by making results lost in reams of unrelated results.