Economist Eugene Fama in a selection from a fascinating interview opines that:
Basically, the institutions that are con- sidered to be too big to fail have their debt priced as if it’s riskless, which gives them a low cost of capital and makes it very easy for them to expand and become an even bigger problem. Plus, everybody now accepts the assertion that they are too big to fail, which creates a terrible moral hazard for the management of these financial institutions. Business leaders won’t consciously tank their com- panies, but too big to fail will push them toward taking more risk, whether they realize it or not. I don’t think Dodd–Frank (the Dodd–Frank Wall Street Reform and Consumer Protection Act) cures that moral hazard problem. Even if lawmakers could devise the perfect regulation for such a cure, the chance that it will be implemented by the regulators in the way designed is pretty close to zero.
The simplest solution would be to raise the capital requirements of banks. A nice place to start would be a 25% equity capital ratio, and if that doesn’t work, raise it more. The equity capital ratio needs to be high enough that a too-big-to-fail financial institution’s debt is riskless, not because of what is essentially a government guarantee but because the equity ratio is very high.