This article is long, but it's totally worth the read. I think everyone should read it, actually. RFID is going to play such a huge part of our lives in the coming years that we all need to be aware of the risks and potential security dangers. I really like the one quote in the article:
Give the article a read if you have time, it will really give you a new perspective on this upcoming technology. :-)
The world of RFID is like the Internet in its early stages," says Ari Juels, research manager at the high tech security firm RSA Labs. "Nobody thought about building security features into the Internet in advance, and now we're paying for it in viruses and other attacks. We're likely to see the same thing with RFIDs.