If there are 5 wells and an owner of 1 well poisons 4 of them, they are able to charge more for the remaining clean water, and possibly acquire money for a commodity which was previously available for free, by increasing scarcity. In a private government concerned only with maximization of income of its owners or investors such pathological outcomes are possible. In the U.S. idea of a republic it is usually thought there should be a public government concerned with the maximization of happiness of residents, something which many libertarians or anarcho-capitalists do not agree with.