"Timestamps could be used to map customers to their precise purchasing behaviors with infinite granularity."
Between debit cards and loyalty cards, this is pretty much already happening. In the US, I see few people using cash without the loyalty card (because the loyalty card gets you a discount.)
Of course, the remainder of your comment would require this new technology. And would be creepy as hell.
The difference is you could be identified when you arrive versus when you are checking out. Your experience within the store would change. For example, if you spend a lot of money then you might be greeted with VIP welcome wagon. If you don't, you might be greeted with a cold shoulder.
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.
Between debit cards and loyalty cards, this is pretty much already happening. In the US, I see few people using cash without the loyalty card (because the loyalty card gets you a discount.)
Of course, the remainder of your comment would require this new technology. And would be creepy as hell.