Holy cow. When I read this in Clemens Vasters' blog, I thought, "Hey, given that all computer is based on physical security, this means we're pretty screwed."
A security researcher has revealed a little-known vulnerability in many locks that lets a person create a copy of the master key for an entire building by starting with any key from that building. [...] After testing the technique repeatedly against the hardware from major lock companies, Mr. Blaze wrote, "it required only a few minutes to carry out, even when using a file to cut the keys." [nytimes.com -- free sign-up required]