Edward CastronovaThe European Central Bank has issued a report on virtual currencies. There's nothing to worry about, they say. Virtual currencies are no threat to the real world, since they are small and not enmeshed with the real economy in a significant way. This reminds me of a story. An optimist falls off a 30-story building. Passing the 15th floor, he says "So far, so good." When he hits the ground he says "Wow, I didn't see THAT coming."