They have to be selling the data because the advertisers certainly aren't using it. I turned of my adblocker just to see what kinds of adds I was being offered.

I could get cheap heating gas from a company 200 miles away, buy crap I didn't need including "magic" amulets and my favorite: get the exact degree that I already had from the exact university that I got it from.

Facebook knows I am an atheist with a college degree, the school I went to and what degree I got there and my current city, so they should have been able to filter all of those out. None of that information was tricked out of me, btw, I added it all myself.

Oh and the rest of the ads were 90% shitty dating sites (because, I suspect, that good dating sites don't need to advertise) more than half of which were obvious scams (again, I have a college STEM degree, don't show me the stuff that hopes to just get stupid people to sign up).

Facebook does allow you to opt out of any given add or all ads from that company but they don't even allow you to opt out of ads for a particular group.

So yeah, I hope Facebook is selling the information because I have no idea what else the use it for.