Big woop? you just said its highly doubtful they have any idea about your demographics, I explained you how they can easily do that and much more like know your race and income bracket.

The days of just targeting you based on the content site are over, now demographics and your search/click history plays a role too.

Because their accuracy is abysmal.

Maybe they have a few percent better accuracy than guessing at random. And that might be worth a few billions. But on an individual level they just don't have the slightest clue.

edit: State of the art tracking seems to be "look at what products user x has looked at, show the exact same product everywhere after he/she probably bought it".

Now if you do have and use a facebook account that is another thing.

> Because their accuracy is abysmal.

Can you give some sources for your claim?

Not really, but it is kind of obvious. I have a very weird setup which would be quite easy to fingerprint (probably a handful in the world and likely only one in my town uses my display setup for one). I am the only one using my devices and noone else is using my IP (and I don't switch IPs either) and I don't use any ad-blockers. Yet ad networks haven't got a clue, often even get gender wrong. (And as a male i interested in tech that should probably be the easiest scenario imaginable)

I guess the most tangible data point is when google allowed you to look at what google thought if you (gender, age, interests etc.) and how bad they are at it unless you actually use their services.

It is obvious they would be far better of targeting sites than users without accounts. But that is not where their competitive edge is so they downplay that. Also, I guess they are big enough to not care about people without accounts.