Stocks sunk below 7000 at the open today, extending a global selloff fueled by trouble in financials. The Dow was off 161 points by mid-morning, while the S&P tumbled 2.5%, the Nasdaq 1.9%. Bad news abounded, with HSBC saying it planned to limit US lending, AIG’s bailout expanding, and Warren Buffett telling investors that the economy would be in “shambles” this year. (More stock market stories.)