Interesting concept. I don't know if RFID theft is rampant at this time, but I do believe that it would be easy. I used to gain access to a building with it--if you want into that building, just blast any employee approaching the door with the RF interrogator signal and their card will return their code and presto, you're in.

Probably we will need to do something to protect us in the future. Afraid that using a RF cloak produced by my phone will make the battery dead or require larger batteries. But still, better than not protected.

I still advocate identification using biometrics over RF. RF is fine for inventory, but not anything secure.