After the financial crisis, a focus on safety and soundness was good medicine for the financial system. New bank liquidity and capital policies, among other initiatives, strengthened a debilitated patient. The banking system is now stronger, with more liquid assets and better underwriting standards. Despite good intentions, however, politicians and regulators constructed an expansive and untested regulatory framework that will have unintended consequences for liquidity in our financial system. Taken together, these regulatory changes may well fuel the next financial crisis as well as slow U.S. economic growth. The Volcker Rule, for example, bans proprietary trading by banks. The prohibition, when combined with enhanced capital and liquidity requirements, has led banks to avoid some market-making functions in certain key equity and debt markets. This has reduced liquidity in the trading markets...

http://www.wsj.com/articles/how-the-next-financial-crisis-will-happen-1433891718