For years, Tian Jia made the kind of returns on his money that investors in the rest of the world could only dream of. The 29-year-old Beijing-based programmer had $440,000 on deposit at the Hong Kong bitcoin exchange Bitfinex until last week and, on good days, would wake up to find a couple thousand more dollars in his account than when he went to sleep. The earnings came from lending his dollars to traders who wanted to leverage their bets. The exchange allowed lenders like Tian to set their own rates, and he says margin traders paid as much as 700 percent annualized interest to borrow dollars. At times, he earned ... (full story)