The euro may well be on the road to a chaotic collapse, taking some of the world’s biggest banks with it. A currency war may break out between Japan, the U.S. and Europe. Printing money has run out of steam, but there is still little sign of the global economy returning to the kind of growth rates it saw before the credit crunch. But in the long term what they should perhaps be most worried about is losing their monopoly on issuing money. A new breed of virtual currencies are starting to emerge — and some of the giants of...