This sums up my problem with the article. People who are concerned about inequality (I can't speak for Piketty in particular because I haven't made it very far

This sums up my problem with the article. People who are concerned about inequality (I can't speak for Piketty in particular because I haven't made it very far through his book) are not necessarily concerned that workers are receiving less than their marginal product because their employers have stolen the remainder via "class power." On the contrary, we're concerned that workers are receiving their marginal product, which is a "just" wage from a purely economic perspective, but which is no longer (for the vast majority) a wage that affords a decent life. At least that's true for people like me who put more stock in the economic explanation for inequality (technology + globalization) than the political explanation.