Bruce Schneier is the designer of the Blowfish and Twofish encryption algorithms and the author of "Secrets and Lies", one of the best books on Security that I have read. He is, in my opinion, one of the few people out there who really understands security. Here he explains in easy-to-understand terms why a National ID card is a bad idea.
My favorite quote: "There is more security in alert guards paying attention to subtle social cues than bored minimum-wage guards blindly checking IDs"