Yglesias links to Steve Randy Waldman's post on negative interest rates. A commenter at interfluidity writes:

“Land owners at full gluttony can eat no more than a small fraction of potential output, and they cannot store the surplus. Technology and population are stable, but land owners face negative real interest rate. There are laborers who would be glad to borrow the surplus bread, but they have no capacity to repay. The real interest rate on the bread lending market would be -100%.’

SRW, this observation seems too close to Marx’s prediction that capitalists capturing more of the surplus value will eventually experience falling profit, while workers become more exploited. It seems the world has been in this place before, and we need to save capitalism from destroying itself.