unless they're shut down by the company that installed them, RFID tags can be read

Zombie RFID tags may never die - News - ZDNet:
"Item-level tagging is some way off yet, mainly due to cost rather than retailers' lack of enthusiasm but, when it does kick off in earnest, it's worth putting money on consumers being at loggerheads with retailers over when exactly to switch off and kill the chips.

RFID tags can be read--either by a store or by an unrelated third party--unless they're shut down by the company that installed them in the product. "

While a consumer might quite fancy the idea of walking up to the checkout and having his new $9,000 plasma-screen TV scanned instantaneously, he might not be so pleased that any passer-by with a reader can find out what he's got in the back of his car. He may also just not like the idea of a supermarket being able to scan his goods after he's left the store.

But when should the tag's tracking powers be turned off? Kill commands, as they're known, do exist. The idea is that when a shopper passes a certain point, any active RFID chip essentially shuts itself down (German supermarket Metro tried similar technology with its RFID rollout and was rather red-faced to find its kill commanders were more like a nasty-kick-in-the-shins commands).

The question remains: why would we want to keep the tags active once we've left our local Tesco and should retailers be allowed to?…

http://zdnet.com.com/2100-1103_2-5214648.html?tag=zdaresources