They are not terribly organized, nor do they have spokespersons, or leaders, but I believe that at the heart is that financial institutions got away with fraud and mayhem a few years ago, resulting in people loosing their retirements, people foolishly buying into scam mortgage loans, etc., and bailouts using tax-paper money for banks whose CEOs should have been prosecuted, not rewarded for scamming Americans.
Many have political motives that include a more libertarian view, where the fed. reserve, also responsible for the bailouts, is done away with, and that less rather than more government is in place in the USA.