Imagine a magic chalkboard that can never be erased, and is very large, and you can write on it with an infinite number of colors of chalk. No two pieces of cha

Imagine a magic chalkboard that can never be erased, and is very large, and you can write on it with an infinite number of colors of chalk. No two pieces of chalk are the same color. Put this chalkboard in a public space and let people write on it with their uniquely colored pieces of chalk. What uses could such a chalkboard serve? This is how I like to imagine blockchains. The magic chalkboard and a blockchain solve, or fail to solve, the same problems.