Meta CEO Mark Zuckerberg, left, and Microsoft CEO Satya Nadella. Getty Images | Reuters The more than 20,000 potential job cuts Meta and Microsoft revealed on Thursday, months after Amazon announced its most widespread layoffs ever, may only be the beginning. The same companies that are collectively spending hundreds of billions of dollars a year to build out artificial intelligence infrastructure to meet soaring demand for AI services are seeking efficiencies from AI by slashing head count. They're also still trying to rightsize from the pandemic-fueled overhiring. Many economists and industry experts are fearful that a labor crisis may be upon us today — not coming sometime in the future — given how quickly AI is sweeping across corporate America.…