> Amazon has also learned something about me I didn't necessarily need to tell them -- ie, that I'm privacy-focused.

Exactly, and it turns out privacy-focused people tend to be relatively self-similar in many ways and, at least back in the day, were easier to advertise to.

Now, Amazon (or whomever) still doesn't know your name, but they are still targeting you and, what I found super interesting, is the fact that it was often more effective targeting than if the person was just part of the bulk of the population. It's kinda like if the system observed all the nonconformist teens like to wear Doc Marten's.