Millionaire and billionaire CEOs say thousands of laid-off tech staff just did 'fake work'

• Silicon Valley founders and investors are debating what constitutes real work in tech.
• That's amid the biggest shedding of jobs in the industry's history.
• Investor Keith Rabois last week said firms had over-hired engineers who do "fake work."

If you're not building or coding what, exactly, are you doing? 

That's the question posed by certain members of the Silicon Valley elite who are attributing layoffs to a boom-time phenomenon: over-hiring and "fake" work.