The analogy at the end is the point:
A real-world analogue would be this scenario: You drive to Home Depot and walk in. Closed-circuit cameras match your face against a database of every shopper that has used a credit card at Walmart or Target and identifies you by name, address, and phone. If you happen to walk out the front door without buying anything your phone buzzes with a text message from Home Depot offering you a 10% discount good for the next hour.
*shudder*