In fact, I used to work for a company that does exactly this and has done it for many years now. They just last year (or thereabouts) released their newest ver

In fact, I used to work for a company that does exactly this and has done it for many years now. They just last year (or thereabouts) released their newest version that is supposed to run over all the various bits o' data it collects automatically and generate ads tailored to every customer. (www.sitebrand.com if you're intersted, or just google "web personalization" and you'll find a bunch of their competitors, who also do a bunch of very neat things in this space.)