For critics of mega-banks, the reports are the latest sign of big banks' ability to defy regulation, engage in dubious business practices and face few consequences.

In a British court last month, a former Nigerian governor pleaded guilty to pilfering $79 million from state coffers, funneling it offshore and buying six properties in the U.S. and UK. The banks he used to move the illicit money? HSBC, Citibank, Barclays and Schroders.

"Banks get hauled up by the regulators for failing to follow the law, promise to reform, and yet a few years down the line they're caught doing the same thing," said Robert Palmer of the anti-corruption group Global Witness. "I think for this to change we need strong penalties for when the banks get things wrong, and in the worst cases, jail time for individual bankers."

Four current Federal Reserve presidents, meanwhile, are arguing that the Dodd-Frank reforms have not eliminated the "too big to fail" banks, according to a Bloomberg Businessweek article published last month. Despite measures in the legislation banning further bailouts, traders, analysts and bankers simply don't buy it.

"Markets have come to believe that what the government did in 2008 and 2009 isn't a one-time deal," Kevin Warsh, a former member of the Federal Reserve Bank's Board of Governors, said in a March television interview with Charlie Rose. They think "that the government will somehow come to the rescue of these big financial firms."

The result is a half-dozen massive banks that remain so large that their collapse would cripple the U.S. economy and force another government bailout. As a result, the behemoths function as a de facto oligopoly. The sheer size of the banks - and the theoretical government backing that they enjoy - make it impossible for the country's roughly 20 regional banks and 7,000 community banks to challenge them.

BIGGER AND BIGGER



The country's biggest banks are getting bigger.

Five U.S. banks - JPMorgan Chase, Bank of America, Citigroup, Wells Fargo and Goldman Sachs - held $8.5 trillion in assets at the end of 2011, equal to 56 percent of the country's economy, according to Bloomberg Businessweek. Five years earlier, before the financial crisis, the biggest banks' holdings amounted to 43 percent of U.S. output. Today, they are roughly twice as large as they were a decade ago relative to the economy.

The four Federal Reserve presidents -- Richard Fisher of Dallas, Esther George of Kansas City, Jeffrey Lacker of Richmond and Charles Plosser of Philadelphia -- have expressed concern that such a concentration of assets in the banking industry threatens the financial system.

In a scathing essay published in March in the Federal Reserve Bank of Dallas' 2012 annual report, Harvey Rosenblum, the bank's head of research, called for the government to break up the country's largest banks. Rosenblum argued that only smaller banks - not the increased capital requirements, stress tests and other measures in Dodd-Frank - will prevent another crisis.