Bruce Schneier talks about how the mechanics of privacy changed since the advent of social media, who holds control and power in the new arena, what are real issues and what are just generational differences in dealing with them. He has a lot of good analogies to make his points. 🙂
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.