The perplexing thing about the cult of overwork is that, as we've known for a while, long hours diminish both productivity and quality. Among industrial workers, overtime raises the rate of mistakes and safety mishaps; likewise, for knowledge workers fatigue and sleep-deprivation make it hard to perform at a high cognitive level. As Solomon put it, past a certain point overworked people become "less efficient and less effective."
If anyone thinks that our current working culture is rational, remember that any business that expects regular long hours and overwork is ignoring all the scientific research on productivity.
Photo by Evan Blaser and used under a Creative Commons licence