On Aug 7, 2013, at 1:24 PM, Scott Brim <scott.brim@xxxxxxxxx> wrote: > I keep my passport in a "cage" when I'm not handing it to someone. > I'm not concerned about my phone. Likewise. The point being, handing everyone in IETF an RFID tag probably doesn't have new privacy implications for most of them, and giving them a faraday cage, as was done in Hiroshima, addresses the remaining implications for those people who do not carry powered-on cell phones or laptops for privacy reasons. If you carry a powered on cell phone, I don't think you can argue that carrying an RFID tag with a simple number in it makes things any worse. Actually, the main argument I'd make against IETF RFID tags is that it's more plastic to throw out.