I do believe that, but I also wonder... Retargeting, i.e. ads of particular product stalking you everywhere you go, is the single method that so far guarantees I just won't buy the advertised thing, out of pure spite. It's also the one aspect of ad experience that I see regular people noticing and getting angry about. I wonder how big an impact of such reaction there is on retargeted ad performance, and if ad people even factor it into their calculations.