What does Utilitarianism suggest about the distribution of wealth in society? Why do Libertarians object to Utilitarians on this point?
Neither Utilitarianism nor Libertarianism are monolithic, and thus different representatives of these traditions advocate somewhat different economic systems.
In Libertarianism, absolute freedom of the individual is paramount with limited regard for how that freedom impinges on other people. Grounded to a degree in Mill's "harm principle," most libertarians want to minimize government. With regard to distribution of wealth, Libertarians can fall into multiple camps, ranging from extreme "free market capitalists" such as Ayn Rand, who see wealth inequality as a natural effect of differential ability and drive, to libertarian socialists who wish to abolish private property completely.
Utilitarianism, or its contemporary incarnation as Consequentialism, argues that the central tenet of ethics and political theory is the maximization of happiness, in the form of "the greatest good for the greatest number". This emphasis on the "greatest number" suggests that great concentrations of wealth in the hands of a few people is a problem, as it may increase the happiness of a few people at the expense of the relative unhappiness of many, leading to a far lower overall degree of happiness than a more equal system. Many free market capitalist Libertarians object to any form of income redistribution as interfering with individual liberty.