You might want to catch Martin Kaste's piece tonight on All Things Considered. It's about all the information you can inadvertently give out about yourself when you use "smart cards" containing RFID (that's Radio Frequency Identification) tags — which many of us do. Martin starts with a demonstration, using the pass card that gives him access to his office. Even though the card is stored inside his wallet in his pocket, a graduate student is able to use a tag reader to obtain the password to the office door. Privacy advocates have been complaining about this technology for years, and now California is considering a proposal to allow people to turn off such cards if they want.