I'm not sure what scientific bar of proof you would need to see passed, but Google stalks users and targets them because it makes them more money. The ads perform better. Their systems fall back on context, when they can't do the more lucrative stalking.
I think it's a downward spiral, it only works because each player is forced to play along due to fundamentals of game theory.
So what we are seeing is that the methods become more ruthless every day, but everyone needs to conform, and it's a race to the bottom.
The end result is spending-fatigue and numbness in response to normal ads that are not hyper-addictive.
I also think it does not really pay off for publishers. It only really pays off for the middle men and those players who sell unethical products aimed at manipulation.
