Ad targeting at Yahoo by Greg Linden.
From the post:
A remarkably detailed paper, “Web-Scale User Modeling for Targeting” (PDF), will be presented at WWW 2012 that gives many insights into how Yahoo does personalized advertising.
In summary, the researchers describe a system used in production at Yahoo that does daily builds of large user profiles. Each profile contains tens of thousands of features that summarize the interests of each user from the web pages they have viewed, searches they made, and ads they have viewed, clicked on, and converted (bought something) on. They explain how important it is to use conversions, not just ad clicks, to train the system. They measure the importance of using recent history (what you did in the last couple days), of using fine-grained data (detailed categories and even some specific pages and queries), of using large profiles, and of including data about ad views (which is a huge and low quality data source since there are multiple ad views per page view), and find all those significantly help performance.
You need to read the paper and Greg’s analysis (+ additional references) if you are interested in user profiles/marketing.
Even if you are not, I think the paper offers a window into one view of user behavior. Whether that view works for you, your ad clients or topic map applications, is another question.