Billionaire bosses like Jeff Bezos and Reid Hoffman denounce work-life balance—and some think working nonstop is key to success

Launching a billion-dollar business or rising to the top of the C-suite requires making some sacrifices, and often, downtime can be in short supply. CEOs are divided on how they feel about work-life balance, but many seem to take issue with the concept itself. And Amazon founder Jeff Bezos is set on redefining the notion on his own terms in leading the retail giant that just dethroned Walmart as the No. 1 company on the Fortune 500. 

“I don’t love the word ‘balance’ because it implies...