By strict definition, the United States is not a Capitalist-Democracy as some have stated; we are instead (or we were founded as) a Capitalist-Constitutional Republic. These go hand-in-hand -- you cannot have economic freedom without political freedom, and vice-versa. Democracy, or majority rule, is antithetical to the exercise of individual Rights. To say that the US functions democratically in the sense that it is a "people's government" is correct. Unlike a democracy, a Constitutional Republic, on the other hand, insists upon the safeguarding of individual Rights.
Capitalism (and not what the media and the bulk of the world seem to think) requires a true level playing field so that competition can occur, where no one and nothing is favored, or the playing field "tilted" by any government or elite; if General Motors fails in the market, they go under, period. Products and services survive because they have withstood the test of a level Free Market. People have purchased or invested in those goods or services, they have in effect, shown their approval by spending their money, or "voting with dollars." People get rich under a capitalist system because they have created wealth by bringing these goods and services to the market, not because they have stolen these things from someone else (in which case they would have violated someone else's Rights to property, and should be justly prosecuted, if the Rule of Law is still intact.)
Oligarchy, or rule by the elite, may be what the US government has devolved into, but that is more a reflection of the failure of our Legislative and Executive Branches of Government than to the economic system of Capitalism. By the government itself continuing to upset the balance of power and destroy representative government, our economic and political freedoms continue to diminish, and those in government grow tyrannous. It's not Occupy Wall Street; it's Occupy Washington.