In the latest 5by5 Talk Show John Gruber and Dan Benjamin speculate how EasyPay in the Apple Store 2.0 app works. EasyPay is a feature that allows shoppers to scan an item’s barcode and complete a purchase via their iTunes account without any interaction with the shop’s staff.
John and Dan are puzzled by how Apple prevents someone from just walking out without properly scanning and purchasing an item.
My wild guess would be the following happens: The barcode contains an RFID chip that will allow sensors at the exit to tell when an item is removed from the store. The barcode also contains an ID that is associated to this RFID in the store’s inventory system. When you scan the barcode and purchase an item, the RFID associated with that item is cleared to leave the store and will therefore not raise an alarm.
Maybe that’s one reason this only works in US stores right now.