Bitcoin cash tripled in two days -- and nobody knows why

Bogdan Cristel/Reuters If you think your portfolio has put on a show since the end of the Great Recession, it's probably just a blip next to the returns of cryptocurrencies over the past couple of months. Since the year began, bitcoin has risen by more than 300%, while digital currency Ethereum, the second-largest cryptocurrency by market cap, has vaulted higher by almost 3,900%! No, that's not a misprint -- that's a 3,900% return on your investment in less than eight full months. Since the year...