Given that our fledgling company is interested in RFID we follow the space pretty carefully. The technology is good, although developments to date have focused more on functionality and less on the security of the data. This has led many to don their tin foil hats and proclaim that ‘the Government’ wants to/can/will track each of our every moves using either the shirts we buy or mandatory implantable chips. Even otherwise sane tech observers have fallen prey to the Chicken Littles.
That’s not to say that there is no problem with the current RFID security situation; there are plenty of issues which need to be addressed. (To my eyes those issues translate to opportunities. 🙂 ) For a reasonably sane overview of some practical effects of the lack of security you should read Annalee Newitz’s article in Wired.