I figured that since a lot of people responsible for these systems read HN regularly, and I haven't got any satisfactory replies on StackOverflow, so I should ask this here.<p>GMail serves some really good ads on the column on the right of the email text. Same goes for Facebook. The ads which I see on Facebook are often (very) relevant to what interests me. Obviously they preprocess the information available to them. They have a lot of user specific information available to them. So I would imagine they preprocess all of it, before generating any ad recommendations.<p>Does anyone know of what specific algorithms/technique do those systems use? Thanks.
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.
While I can't speak for the specific algorithms they use, you pretty much hit the nail on the head of how they determine what ads to use. GMail is a little different in that Google knows a lot about you in terms of the content of the email and what your current conversations contain, they can then drive specific ads based on those conversations.<p>Facebook knows who you are, your age, your location, what you like, possibly what you dislike, your music tastes, movies, etc... They know who you interact with the most, who you interact with the least and can form patterns of what common interests between you and your friends. They combine all this data to determine what kind of ads will most likely appeal to you. The more you interact with Facebook, the more relevant the ads displayed to you will become.<p>Not sure exactly what else you are looking for here though based on your question. The specific algorithms/techniques they use are proprietary to them and what makes their technology worth the money advertisers will pay (along with the number of users on the platform) to place their ads in front of their users.