Grocery stores are already doing this sort of tracking without the benefit of RFID tags - when you provide your "frequent shopper" id, it makes it possible for the store to monitor precisely what you buy and how often. The question of privacy never surfaces, so you can assume that your friendly grocer is selling the data to heaven knows who. But, unlike this scheme, you at least get some sort of compensation for the data you provide in the way of discounts and rebates.

Digital ID: You shop, they snoop?. ZDNet Feb 11 2002 4:53AM ET [Moreover - moreover...] 

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