> Heh, in the security world, this shows how your traditional metal key is "something you know" (like a password) because it can be copied and many people can know it at once!

If you have a photo of a traditional metal key, you can duplicate it. AFAIK, there's also a numeric representation of the height of each position on the key; if you know that number, you can duplicate the key. A traditional metal key is more like a password than most people think.