Even the most die-hard libertarians I know (which I'm using here as a proxy for the most conservative) recognize one of the fundamental roles of government is t

Even the most die-hard libertarians I know (which I'm using here as a proxy for the most conservative) recognize one of the fundamental roles of government is to account for and price in externalities. The OP indicates that the incentives of corporations driven by a profit motive is not to price in externalities. If not the government, what other mechanisms do you suggest?