cuchulainn said:If you use cash, how does the scanner tell that you're the buyer -- as opposed to the 37 other people within X-feet of the counter who also have RFID stuff in their pockets. Is the store supposed to set up an 20-foot perimeter around each cash register within which only the customer currently checking out can enter, lest some poor shlub looking through the clearance rack 5-feet away gets mistaken for the buyer because he has an RFID key-fob in his pocket?
No, they would do just the opposite and place cash registers within 20' (or whatever useful distance) of each other. That way, they can use the differing signal strength to more accurately determine location. The more registers/RFID scanners, the better. It is analogous to GPS: the more satellites you can connect with, the better your location estimate.
I did not suggest that every cell phone would also be an RFID scanner, I was merely showing that the mating of an RFID scanner with cell phone functionality allows it to access a nearly ubiquitous comms network from remote locations.
The idea of cell phones with embedded RFID scanning tech is, however, a scary thought and do-able. Why not? We already have the equivalent of personal computers integrated into cell phones.
As to the sheer volume of RFID hits, you are right in that a lot would be noise. As I wrote earlier, I doubt its initial use woud be to track everybody all the time, everywhere. Trade-offs would be made as to who, where, & when the tracking would occur. As technology matures, fewer trade-offs need to be made.