A Warning From Buffett About Banks. Buffett, Warren E, Sorkin, Andrew Ross, Banking and Financial Institutions, Berkshire Hathaway Inc, Private Equity, Mergers, Acquisitions and Divestitures, Goldman Sachs Group Inc, Hewlett-Packard Company, JPMorgan Chase & Company, Blankfein, Lloyd C, Dimon, James, Wall Street (Manhattan, NY)