Pedestrians walk by a Citibank branch office on July 16, 2012 in San Francisco, California. - 

When the CEO of Citigroup suddenly resigned, the move caught a lot of people by surprise. But it isn't a newsflash that the country's third-largest bank is struggling. Citi has not come roaring out of the financial crisis like Goldman Sachs or JPMorgan Chase. "The bank was going to be all things to all people and all companies," says Allan Sloan, senior editor at large at Fortune Magazine. The problem, according to Sloan, is that the bank got too big, too complicated, and maybe too generalized to appeal to individual customers' needs. "If you have any idea of what you are doing, you can just go the a la carte route, which a lot of people did," says Sloan, "meanwhile the banks were falling all over themselves trying to make all the pieces work together, which generally they don't."

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