It is with transport cards, namely London's Oyster card that the issue has arisen again with another security hole found by Dutch researchers. They managed to clone an oyster card to a standard building security entry card which uses the same technology. They then travelled to London to test their clone, travelling for a full day on the London Tube with no problems.

Apparently the hardware required to skim the information is relatively cheap and can easily be used with a standard laptop, making RFID cards and passports vulnerable to anyone with know-how and inclination.

More detail about this story can be found in the following article: "Group Demonstrates Security Hole in Oyster Card".