Most of that information exists outside the RFID chip. For example, the E-ZPass system consults a networked database to determine if a driver has sufficient funds in his account to cross the George Washington Bridge and enter Manhattan. In this sense, an RFID tag is a miniature one-trick pony, endlessly sending out the same message to any receiver willing to power it up: “I am product number 5555-39993-2222-888888-24321.” The receiver then takes that number and consults the database to figure out what it’s dealing with. In the most familiar scenarios, that database lookup revolves around identifying the object’s price so that the consumer can be charged for it and identifying its make and model so that the store can replace the item on the shelf.

In one wishful vision of the future, supermarket customers zoom through checkout lanes with full shopping carts, every item instantly charged to their credit cards as a restocking notification is simultaneously sent to the store’s inventory department. The result is friction-free: no lines and no empty shelves. But RFID also opens the door for intriguing changes that involve the application of special filters to the networked database.

Imagine this simple scenario: You download a new pork recipe from the Web and get an instant report on whether you have the required ingredients available in your home. The software simply compares the database of objects nearby with the list of ingredients in the recipe. Here’s a more elaborate version: You consult an online cookbook and ask for a list of all the pork dishes that could be made using the ingredients you have on hand. Or suppose you have a cholesterol problem. Instead of memorizing an endless litany of don’ts or carting around a guidebook every time you go shopping, you simply download a cholesterol filter from your doctor’s office. The next time you visit the supermarket, your handheld RFID reader steers you to foods that will keep your levels in check.

The limited transmission range of radio frequency identification (RFID) chips could serve as a default protection against snooping. A receiver must be within a few feet of a chip to generate enough magnetic energy to release the RFID signal, making long-distance surveillance difficult.

Although privacy activists make RFID sound like yet another invisible chain wrapped around the hapless consumer by the forces of big business, the technology may well grant consumers power in the marketplace. Companies will have a much harder time selling poorly made products if shoppers come equipped with RFID readers that can instantly tap into online review sites like epinions.com. Greenpeace could release RFID filters that flag products made in environmentally friendly ways. Anyone who has ever tried to apply political values to consumer decisions knows that it takes a great deal of effort and research to keep on top of the latest developments. (Did Nike fix that sweatshop problem? Or was that Adidas?) With RFID filters, you could simply download the latest recommendations from your favorite organization and let your reader make the politically correct choices.

Right now, companies exploit a simple fact of life: Most consumers are too busy to make informed decisions about their purchases. RFID-based filtering could make that form of exploitation more difficult. Viewing the future of RFID from this angle, the challenge is to assure public access to databases. The powers that be already have a vast collection of tools available for spying on you—from your credit card purchases to your ATM withdrawals to onboard GPS systems to satellites that can read a license plate from Earth orbit. If they want to keep tabs on your activities, they can do it already, whether there’s a smart label on your sweater or not. (For peace of mind, perhaps RFID tags should include a “kill switch” that turns them off when you leave the store.) But if RFID numbers become a protected part of their manufacturer’s copyright, most of the important consumer benefits will disappear because creating a filter for a brand of milk or a line of sneakers might require a license fee.

 “The fact that a given item is number 123 in the RFID database needs to be legally considered a public fact,” says sci-fi author Cory Doctorow, who also works for the Electronic Frontier Foundation. “If you limit the public’s ability to make a connection between a product and an RFID tag, then all of these filtering technologies become much harder to pull off.” It’s hard to have a consumer revolution if you can’t identify the product you’re boycotting.

If Wal-Mart’s history is a lesson, we’re going to confront these issues sooner rather than later. After all, back in 1984 Wal-Mart embraced another little-known but promising new inventory-management tool. You may have heard of it. It’s called the bar code.

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