Bitcoin is crashing -- upward. It just passed $28,000 and shows no signs of stopping. The digital currency has a market value north of $500 billion. Think Bitcoin is just a fad? It's worth more than Visa (V) or Mastercard (MA). Or Walmart (WMT). Bitcoin passed $20,000 for the first time just 11 days ago. Now it's knocking at $30,000's door. Its rapid rise has been remarkable -- or insane, depending on your appetite for risk. But there's some logic to the run-up: Investors are pouring money into bitcoin and other cryptocurrencies during the Covid-19 pandemic as the Federal Reserve sent interest rates near zero (and ... (full story)