(no subject)
I always assumed this was because I'd tripped some Mysterious Neural Network thing somewhere Deep In The Algorithm, but it's actually a lot simpler: "remarketing" is an option that a lot of web-advertising companies support, and it basically just means that rather than targeting by location or demographic, you say you want to try to show your ads to people who have been to your website or viewed your product lately.
That's both creepier AND less creepy than I assumed. Creepier because of the tracking it implies, but less creepy because - an advertiser wanting to remind me of a thing I did actually did before makes a lot of sense and is kind of something I almost want, being-advertised-to-person-wise.