I love how everybody is so busy about mining your behavior for ad tracking data and then like 2/3 of the ads I actually see are utterly irrelevant gut doctor / toenail fungus / 17 Most Embarrassing Topless Celebrity Moments crap.
(I think the reality is that they're mining that data to identify a small number of people susceptible to high-value scams - like getting addicted to an F2P mobile game and spending $1000s on it - and the rest of us just get generic infill)