Someone pointed out that Facebook doesn’t sell user data, that’s the family jewels which they carefully guard, instead selling the opportunity to advertise to curated demographics.
They do track you around the web, and through your phone quite aggressively, however. They guard the actual data, but sell the use of it causally.
Would you want to block Mazda from running ads before car videos on YouTube rather than Mickey Mouse videos?
Absolutely. First, I want to see a world that isn't warped by predictions of my behavior, and second, for the minuscule value of seeing a Mazda ad over a Mickey Mouse one (which on the whole, in my experience has been zero or negative), I'd rather have the privacy.
If I am searching for car videos, take a chance and show me a car ad over a Mickey Mouse ad.