Arphid Watch: Leeches and Ghosts:
“In this study we show that the modeling predictions are quite accurate. We show how to build a portable, extended-range RFID skimmer, using only electronics hobbyist supplies and tools. Our skimmer is able to read ISO-14443 tags from a distance of 25cm, uses a lightweight 40cm-diameter copper-tube antenna, is powered by a 12V battery–and requires a budget of $100. We believe that, with some more effort, we can reach ranges of 35cm, using the same skills, tools, and budget.”
“A German hacker used a simple PDA, equipped with an RFID read/write device, and changed product prices in a grocery shop using a software he wrote. He managed to reduce the Shampoo price from $7 to $3 and go through the cashier without incident. Supermarket checkout trials held by NCR corporation showed that some clients standing at the cashier paid for groceries held by clients standing behind them in the queue.
and yet one more reason why one cannot really trust rfid tech.