U.S. Sen. Elizabeth Warren (D.-Mass.) said Wednesday that an expanding cryptocurrency market could pose a threat to the U.S. financial system if a proper regulatory framework isn't put into place. In an interview on Bloomberg TV, Warren also expressed concern about Federal Reserve Chairman Jerome Powell, suggesting that she was skeptical about reappointing the head of the central bank because of what she sees as a soft approach to regulation. Commenting on the crypto market, the senator compared the asset class to certain markets ahead of the 2008 financial crisis, saying she doesn't want "the U.S. taxpayer to get called on" to backstop another failing financial market. Warren argued that the crypto market could approach that dangerous area "the bigger it gets and the more it stays outside" the financial regulatory structure. The senator, who has been an outspoken critic of cryptocurrencies, comparing them to "snake oil," acknowledged some potential