QUOTE (eidolon @ Sep 14 2009, 01:43 PM)

RFIDs aren't complicated at all, from what I know about them. Passive ones require a reader to pick up the stuff that's magnetically stored on them. Active ones are powered and actively beam out their info to something that's capable of reading it. Strong magnet and hit it with a hammer.
I just wrote a paper on RFIDs and electronic tracking for one of my computer classes, so, here's my .02

.
Passive RFIDs do transmit their info, they don't have an internal power source so they use the incoming "ping" signal to power the transmission, due to the low level of power involved their range, now, is usually no more than 3 meters, however there have been instances of readers picking up signals from passive RFIDs up to 50 feet away, it just depends on how strong the ping signal was, the stronger the ping, the stronger the transmission. I believe that this design flaw may have been fixed in the newer generations of RFIDs, allowing only VERY weak signals, only a few inches in some cases like the ones in the new U.S. passports, so all this could be a moot point.
Just a while back there was a big (in public privacy advocate and computer circles) controversy about Gillette putting permanent RFIDs in their Mach line of razors, thereby making it possible to monitor who their customers were. That policy has since been discontinued due to public backlash. That does not mean others are not doing the same though.
Not all RFIDs are deactivated by stores. Just the security/inventory tracking ones. It has been proven that you can follow someone home by tracking a RFID tag on something they just bought.
The idea in Shadowrun, or so I've gathered, is that a person can go to a Stuffer Shack and pick up what they want then have the sale automatically debit it from the account through their commlink (if their gear is configured for such a transaction). This would mean that the tags in your stuff would still be active when you left the store. I've also gathered that the RFIDs in your food would be destroyed during digestion, which means there would be a period of time where it could still be read from inside you.
As to destroying or wiping them, yeah, a microwave oven works, or a strong magnetic field. I don't think the hammer example would work in Shadowrun, the RFIDs are (as someone already mentioned) nearly microscopic.
Here are just a few examples of what someone can do with
RFID Tags.Edit: To the management: I realize that you have set up this system to make it easier for laymen computer users to post links, however, I actually know how to do so myself and your software keeps screwing with me if I don't use "Quick
Edit" or "Quick
Reply", and your link insertion tool keeps giving me error codes when I try to use it! Just thought I'd vent a little, sorry.