One day, not long from now, virtually any store, restaurant, or business may be able to identify you, note what clothing you're wearing--and possibly even detect how much money you have in your wallet--as you enter the establishment.

With little fanfare the new technology that could make this possible, called RFID, or radio frequency identification, is rolling out on a massive scale. RFID tags potentially could be placed in clothing, laptops, even currency. The chips that run RFID tags are barely detectable flakes of silicon, some no bigger than a grain of salt. Each tag uses radio frequencies to transmit a code that uniquely identifies the tag.

How might the tags identify you? If, for instance, you buy a sweater using a credit card, your name could be forever linked with that particular plaid cardigan.

Alien Technology, an RFID tag maker, projects that within three years the company will sell 10 billion RFID tags a year and that the cost of a single tag will drop below 5 cents, cheap enough that they may start to appear in most products.

RFID readers within about 15 feet of some tags can pick up their signals. Global databases will let businesses keep track of every location where an RFID signal has been read.

That's what worries privacy advocates: how easily companies can read the tags and keep logs, identifying and profiling consumers long after the tagged products those consumers bought leave the store. "In the future, [RFID] tags could take away from your ability to move about anonymously," says Katherine Albrecht, the founder and director of CASPIAN (Consumers Against Supermarket Privacy Invasion and Numbering), a consumer group opposed to customer profiling through companies' use of supermarket discount cards.

While RFID has the potential to identify us all, the technology's supporters say that is not its primary purpose. It exists to ensure that store shelves are constantly stocked with razors, batteries, and blue jeans. And there's reason to be optimistic that this emerging industry will do the right thing when it comes to privacy.

Acutely aware of the privacy concerns connected with RFID technology, an advisory council associated with the Auto-ID Center, an RFID research group based at MIT, has proposed an RFID bill of rights for consumers. Among the group's recommendations is to disable tags as they pass through the checkout area.

Companies will choose to protect consumers' privacy because they don't want to alienate buyers, says Kevin Ashton, executive director of the Auto-ID Center. "Most companies are not evil, cackling maniacs trying to rip people off. They're just trying to do a good job."

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