Wouldn't it be nice if there was a "bought it already" app? Probably bad for google though.The ads will be based on your search history. I keep getting stuff I've searched for work and hunting boots I got for my son. They clearly aren't correlating purchase history, but try to keep it relative.
The only adds that really annoy me are pop up adds that make another window. Pay sites is what I don't do so I'm with elmer_fud on letting the websites make their add money to keep it free.I use firefox browser and use their free adds blocker so I dont get any of the adds.