"Mr Balin helps crack that problem. In the first few seconds a visitor spends on SmarterTravel’s site an algorithm builds a picture of them. Click speed helps: window-shoppers tend to skip quickly between pages, serious buyers ponder for longer. Other data including the time of day, number of previous visits and location are important. The algorithm spits out the probability that the user is a potential buyer. With that, it calculates the revenue gains and risks (of distracting shoppers) associated with showing adverts. The site is adjusted in a few milliseconds."
Damn that's crazy.