My wife and I use a credit card with the PayPass feature. Tap the card on the reader, the green lights glow momentarily, there's a beep and the purchase is paid for. Fast, easy and possibly not secure.
My wife was paying for a purchase today and the the card reader flashed and beeped while my wife's card was still inches distant. The clerk said that the store card reader was more powerful than most and was causing some customers a little grief. Occasionally, the reader would complete a transaction while the customer's card was still in the customer's purse. If the customer has two cards and both have RFID, radio frequency identification, sometimes the wrong card is activated.
The clerk told us she knew a lady who, after pumping gas, got her card out to pay for her purchase. When she walked by the next pump, her card connected with that pump's card reader. She almost paid for a stranger's gas.
If I hadn't seen my wife's card talk almost remotely to a store card reader, I'd have found the gas pump story more urban legend than truth. But after what I witnessed, I'm not so sure how secure these RFID cards really are.
Check out the story posted by CBC News: New credit cards pose security problem.