Some people bug out hardcore over privacy concerns. I can see how it's justified in certain situations, but I really doubt RFID is the next hidden tracking device for consumers...as of right now. Anyways, if you're really paranoid, you could make like Mike Sklar and built a faraday cage around the pocket. What the hell is a faraday cage you ask? That's what wikipedia is for. Anyways, it's simple to make one by ripping out a pocket in your jeans or khakis and replacing it with a soft material with a conductive metal inside it. This will keep those nasty RFID tags from being read and your privacy intact.
RFID Pocket Replacement [WMMNA]