In case you haven't done this yet, one way to gather some insight as to how they are targeting their ads is to take a look at the ad buying pages for the respec

In case you haven't done this yet, one way to gather some insight as to how they are targeting their ads is to take a look at the ad buying pages for the respective sites. In the past (it may have changed) Google AdWords were solely based on keyword targets - that tells you they are probably processing text on the page rather than pulling from any user database they may have. Facebook, on the other hand, basically gives advertisers their pick of profile information, to a surprising degree of accuracy (eg. friends of people who like X band) - it is pretty obvious how they might provide that level of accuracy based on the data available to them.