PHILADELPHIA -(Dow Jones)- There should be a market mechanism, not dependence on regulators, to address the problem of banks being “too big to fail,” said William Poole, former president of the Federal Reserve Bank of St. Louis and senior fellow at the Cato Institute.Speaking Thursday at a conference organized by the Global Interdependence Center and Drexel University’s LeBow College of Business, Poole said there must be creditors - not just stock holders - that are at some risk of loss.