You’ve heard of cryptocurrencies. They’re those computery coins that people began talking about as their prices seemed to explode overnight, turning a bunch of geeks into instant millionaires. Depending on whom you ask, cryptocurrencies are either the beginning of a technological revolution, a Ponzi scheme, the key to financial freedom from banks or history’s greatest scam. Amid the technobabble, the sensationalist headlines and the idealism of crypto fanatics, ...