actually.. if you have a "Speedpass Key" from Exxon, it's RFID.. if you have a Toll Way tag that attaches to the inside of your car, it's RFID and can be read over 300 feet away @ 100mph.. various CCs have RFID chips in them.. all US Passports have RFID now.. and with the Real ID act passed, soon all US Driver's licenses will have RFID.. this does not take into account your clothing, all your purchases, etc..
yes, it's a passive device, but the readers are what have variable distances.. i.e. some readers can read under 5 foot.. some readers can read at nearly half a mile.. this is the problem..
this is not as benign as a simple UPC bar code.. this is data mining at it's source.. the DOD has had a plan for the last 7 years, on collecting information on all people within US territories.. this means tracking your movements through RFID..
and implantable RFID chips have been in use for sometime.. i applied to work at Lockheed (Skunkworks) on the X33 project.. and within the paperwork sent to me was a consent to be implanted with an RFID chip.. this was used in addition to a worn badge.. your movements within the complex would be monitored, and readers would allow doors to open, or not.. this was over 10 years ago..
so, the chances are high that there are RIFD chips in current manufactured pistols.. especially, polymer guns.. and, it would be a simple thing to scan a home to find RFID'd weapons.. or ammo..
i'm not sure about how to actually disable RFID chips.. i'm sure if you had a chip laying there you could "zap" it.. (they are about the size of a grain of sand, itself.. but have an antenna and power supply on a larger silicon die)
i know that you can shield it to prevent it being read, with a simple Faraday cage..
the only way to be sure, is to buy a RFID scanner and try to read everything you have.. but, the problem with that is, that there could be variable frequencies and your reader will not read those RFIDs out of it's range..
RFID is a great technology.. but, it's being exploited in a very wrong way..