The granularity I'm referring to is in the nuanced behavior of an individual in the act of shopping. Apparently, the algorithm has established that you follow a pattern of contemplating Cadburry chocolate bar purchases on every visit, well now your Inbox contains a buy 2 get 1 Free Cadburry coupon that only works for you.

Once this is cheap enough that anyone with a high def webcam can consistently track/identify faces, this technology is going to be used by everyone.