This final note comes by way of Businessweek:
The FBI says criminals have found a new way to use stolen credit cards. They scale the roof of a store and wrap aluminum foil around antennas. Stores use antennas to communicate with credit card companies. That foil blocks the transmission, which means stores can't verify whether a card is legit or stolen.
Businesses figure the connection's down temporarily, which happens every once in a while, and approve the transaction.
By the time a business finds out what the card was stolen, the criminals are long gone with the merchandise they bought and the stores ... are on the hook.