Google does this to the worst extent. Even if i didn't search for a website, it still some how knows exactly what websites I've been visiting. Every time I buy something online, I start getting advertisements for that exact product, from the company I just bought it from, across Google search pages and on Googles ads on other webpages. How they think this "targeted advertising works" is beyond me. First of all, if I know I like something already I don't need an advertisement. Second of all, I just bought stuff from that site, you don't need to tell me to go back there if I liked it. Thirdly, the only good thing about ads is showing you something you haven't seen before, not telling me what I've already tried. Fourth, stop watching me bro.