It's not just product advertising, it's also political advertising which gets even creepier in my opinion. The two major outfits in 2016 (BlueLabs for Clinton, Cambridge Analytica for Trump) were spending hundreds of millions on these kind of targeted ad campaigns according to numerous disclosures.
For example, I imagine Team Trump would target the white supremacist crowd (a relatively small % of the public) with one set of ads, and target Rust Belt voters (the key demographic that flipped the election) with trade issues and 'bringing back manufacturing' ads, although the latter group would likely have been turned off by the white supremacist content.
Team Clinton's BlueLabs to be fair did the same thing and yet got much less media scrutiny than Cambridge Analytica. And that's not even counting the much-noted 'foreign influence' (hardly just Russia, Israel and Saudi Arabia have large targeted US-focused PR campaigns running all the time as well).
Creepy dystopian mass surveillance and manipulation in the name of profit maximization, that's what I think of whenever someone talks about Facebook.