For more than a century the heart of the financial world was a physical place called Wall Street, where slips of paper littered the floors and shouted bids to buy and sell filled the overheated air. And the most famous repository of wealth was Fort Knox, where soldiers guarded mounds of gold bars deep inside Kentucky's rolling hill country.
Wall Street and Fort Knox are still there, of course, but their mystique is fading fast. Not even James Bond's nemesis Auric Goldfinger would try to rob the fort anymore; bullion is in a two-decade-long slump. Nowadays, real money doesn't glitter or...