The roots of radio-frequency identification technology stretch at least as far back as World War II, when transponders helped distinguish between Axis and Allied aircraft. Over the years the concept has been greatly miniaturized, landing RFID technology in such settings as animal tags, toll-collection devices, passports, keyless entry systems for cars and wireless credit cards. But perhaps none of these projects will have as much impact for consumers as the adoption of RFID in the supply chains of huge retail stores. Mega-retailers led by Wal-Mart Stores Inc. (WMT) have gotten their biggest suppliers to add RFID chips to pallets and...