How often do you wear that white shirt? RFID (Radio Frequency Identification) tags could answer that question, but who wants to know? And why?
MIT's Emerging Technologies newsletter has an article, "Visualize RFID," with an entertaining animated info-graphic, which describes a possible supply chain, making full use of RFID technology from a shirt's manufacturing to the hanger in your closet. Wal-Mart is apparently requiring all product shipment pallets to have RFID tags on them by 2005. (Note that it's pallets and not individual products - for the moment.) Presumably shoppers will be able to opt-out of active tags in their closets... just the way we all have the choice whether we use our grocery store "advantage" cards.
The privacy implications, if this technology becomes cheap and pervasive, are something to think about. RFID tagged pets? Children? ... I suppose I could use them on my pens and my house keys, though. (And where did I leave my coffee cup?)