linuxmemes

They can probably make assumptions on demographics based on browsing history and interests that are pretty darn accurate with enough data (e.g. someone searching for all three of birth control medicine, a nail salon, and Victoria’s Secret has a pretty darn high chance of being a woman).

That's true, but I think they'd store all that data as part of someone's Google account. Either that or they have a separate type of user just for tracking/targeting.