Microsoft suffered its worst single-day market value loss in company history, wiping out $357 billion in market capitalization as investors recoiled from the software giant's escalating artificial intelligence expenditures.

The stock plunged to close at a market cap of $3.22 trillion by the end of trading, marking the sharpest daily decline since March 2020, according to CNBC. The selloff came on the heels of the company's latest earnings report, which detailed aggressive capital spending on AI infrastructure that failed to convince Wall Street the investments would deliver proportional returns.

The numbers don't lie: This represents the first major crack in the AI investment thesis that has propelled tech valuations to stratospheric heights over the past two years. While competitors like Apple posted record profits by staying disciplined, Microsoft is betting the farm on AI capabilities that have yet to generate commensurate revenue growth.

The market's reaction signals growing skepticism about whether the billions being poured into AI data centers, chips, and talent will actually translate into the productivity gains and new revenue streams that executives have promised. Investors are asking the question they should have asked months ago: When do we see a return on this investment?

This isn't just a Microsoft problem. The entire AI infrastructure buildout—from Silicon Valley to Seattle—is predicated on the assumption that enterprise customers will pay premium prices for AI-enhanced software and services. If Microsoft, with its dominant position in enterprise software, can't make that case stick, who can?

The $357 billion evaporation in a single trading session serves as a wake-up call: The market is done taking AI spending on faith. Companies will now need to show tangible, measurable returns—or face a reckoning from investors who are tired of subsidizing tomorrow's promise with today's earnings.