The free market pundits love to slag on Piketty without acknowledging that his recommendation, after 500-odd pages of facts and statistics, was a free market economy regulated by socialists. The question is not whether market incentives are reliable; the question is whether market incentives are more important than humans. The field of behavioral economics has demonstrated again and again and again that the more distance you put between an actor and the people he's acting on, the less humane he will be. Communism and libertarianism both work great so long as your society's population fits within Dunbar's number. As soon as there are strangers about, crime no longer has a victim. And nearly everyone can abide by the golden rule and the whole thing crumbles the minute someone steps out of line; call it prisoner's dilemma, call it tragedy of the commons, call it what you will libertarianism and communism presume a stable solution to an unstable problem.