Wired has a surprisingly nonhysterical piece on the lack of security in many RFID systems; it’s worth a read. They only miss in one area that we saw, and it’s a picky point: most supply-chain (which is to say, shipping) tags don’t have pricing data, at least not when it comes to biggies like Wal-Mart and the DoD. Those tags hold only a 96-bit number that is associated back to a database entry. They’re not secure per se, but since they’re essentially active bar codes, it matters a lot less in this application than it does in, say, keycards.