"It's like being search bubbled, only from the push end of things rather than the pull end."

That is a good way of putting it.

I also like that you identified "you can tell whether I'll be vulnerable to having one specific thing advertised to me excessively". I got into that in a follow up comment because that's really what targeted ads are about, finding people's irrational purchase triggers because "hey, i'm well informed and this product is great value!" is an expensive trigger to target.