Bitcoin just surged past $8,000 on Tuesday, hitting its highest mark since last July. It tapered off slightly by mid-afternoon, but is still trading at its highest level in nearly a year.What's going on?Bullish experts say the strong showing could signal that bitcoin has a future as a worthy investment opportunity. But the currency's volatile and controversial history has prompted plenty of skepticism.Bitcoin has typically been regarded as risky, said Dan Held, co-founder of Interchange, a company that advises businesses on how to manage their...