Just how much of the financial world could new technology disrupt? Patrick Byrne is trying to push the limits. The hard-charging CEO of Overstock.com has become one of the leaders of the movement to use the "blockchain"—the open-source cryptographic code behind Bitcoin—to do far more than run an invented currency.Last year, Byrne issued the world’s first-ever digital security—Overstock corporate debt—and began creating a new blockchain-based stock exchange to trade it on.