I have written before about security weaknesses in pin-and-tumbler mechanical locks. I suggested that electronic token based systems have a greater capacity to be secure, since they do not rely upon mechanical parts that can be manipulated.
Of course, poorly designed electronic systems can also be breached easily. That was demonstrated in September, in relation to the KeeLoq system used for keyless entry in many cars. Now, another brand (Mifare) of RFID tags have been reverse engineered and found wanting. As is usually the case on matters of physical security, I saw this story first on blackbag.