The TechZone has an article on Radio Frequency Identification Technology(RFID)

There are two general areas where work needs to be done to assure that RFID can be employed without having a negative impact on individual privacy. The first is in the development of the technology itself. With privacy protection as a stated goal, engineering decisions can fulfill that goal. Techniques like encryption, system security, and the ability to easily turn off or "kill" an RFID tag can be made part of the RFID standard. All of these are possible today, but some are considered to be extra features rather than basic capabilities.

How RFID Is Impacting Our Lives