"I ran across this recently and wanted to share it with someone, but didn't know who to send it to, so you're getting it," the reader wrote. "I just received a bulk-mail flyer from Proctor & Gamble with a very interesting feature; namely, what appears to be unique tracking data embedded in the coupon's barcode which tie it to the recipient. There appears to be enough data to track individual coupons, not just geographic areas. Needless to say, there is absolutely nothing anywhere on the flyer to indicate that this 'paper spyware' is present."

The coupon was for $3 off on a purchase of Clairol Herbal Essence hair color. "I almost gave the coupon to a friend who sometimes uses the product until I noticed the barcode had wavy lines and different ink, indicating that it had been individually printed on," the reader wrote. "Once I spotted this, I checked the numbers against the address box and found that both sets of non-address-related numbers in the mailing label also appear on the coupon itself -- one barcoded, the other as plain text only but similar to the remaining part of the barcode."

Sure, it wouldn't be the biggest tragedy if Proctor & Gamble can trace a purchase back to him, but the reader is bothered by the sneakiness of the coupon. "My privacy is worth more than a $3 discount on hair color, but most people wouldn't even know they were selling themselves out if they just clipped the coupon with an uncritical eye," the reader wrote. "I wouldn't be so irritated by this if they came clean about what they were doing -- it's not that different than a supermarket club card, but I know those are being tracked and can choose not to use them. It's the stealth nature of this that leads me to gripe."