Meta shares fell 4 percent – Zuckerberg's fortune dropped $8.9 billion in one day
In one trading day, the market turned AI enthusiasm back on the companies paying the bill: Meta shares fell roughly 4 percent on Friday, September 25, 2026, and Mark Zuckerberg's fortune dropped by $8.9 billion — according to Forbes' real-time calculations, as reported by TechStory. Behind the numbers lies a bigger question: Can AI revenues justify hundreds of billions in infrastructure spending?
What happened on Friday, September 25
Meta shares fell just under 4 percent to $749.26 during Friday trading. The decline hit the company's founder directly: Mark Zuckerberg's estimated net worth fell by $8.9 billion, to $257.5 billion as of 2:30 p.m. Eastern time, according to Forbes' real-time billionaire list as republished by TechStory (TechStory).
That figure is an estimate that changes with the share price during the day, and it is based on Forbes' model of stock and property holdings — not on an actual transaction. But the direction is unambiguous, and the mechanism is simple: Zuckerberg owns around 13 percent of Meta, so large moves in the company's stock translate immediately into large moves in his personal fortune (TechStory).
From fourth to sixth on the list
The decline moved Zuckerberg from fourth to sixth place on Forbes' list, according to TechStory. He was passed by two other tech billionaires: Google co-founder Sergey Brin, whose fortune stood at roughly $259.9 billion, and Michael Dell, who reached around $275.9 billion.
The nearly $9 billion loss was reportedly the biggest one-day drop on Forbes' real-time list that day, and far larger than the roughly $1.6 billion decline that Larry Ellison recorded the same day. The same caveat applies here: the real-time figures are estimates, and the rankings may have shifted again by the end of the trading day.
Why the stock fell: from AI optimism to the AI bill
The sell-off came after a strong run for Meta in September, TechStory writes. As the month went on, investors' attention shifted from the company's ambitious AI strategy to the enormous cost of building the infrastructure it requires — and to the question of whether AI revenues can justify the spending.
That is the core of the story: the same enthusiasm that drove the stock up in the preceding weeks turned on Friday into a question about capital expenditure. Meta is among the companies spending the most on AI infrastructure, and the stock is therefore particularly vulnerable to shifts in the market's assessment of that balance. The market rewarded the AI narrative in September — and on Friday demanded an accounting version of the same narrative.
It should be emphasized: the sources characterize the cause only in general terms of concern about AI spending. No concrete triggering event — a news item, analyst report, or company statement from September 25 — is documented in the available source material.
How big are the numbers in the AI spending cycle?
To put the spending side in scale, TechStory cites Goldman Sachs' estimates: the US hyperscalers — the companies running the large cloud and data infrastructure operations — are on track to spend around $800 billion in capital expenditures in 2026, a significant increase from the year before. In total, the investment bank estimates that global AI-related investment could exceed $1 trillion this year — capital flowing into data centers, computing power, and adjacent technology (TechStory).
Against that backdrop, Friday's share decline appears as a small but clear market response to a question that will be asked again and again: when investments are measured in the hundreds of billions per year, the market demands signs of comparable revenues. Meta is not yet printing those numbers in full — and no sources in this case document that the company released new revenue figures or revised its projections in connection with Friday's fall.
Caveats and open questions
This story rests on secondary sources. All the wealth figures come from Forbes' real-time rankings via TechStory; the Goldman Sachs estimates are also reported through the same channel, not from the bank's original analysis. The figures are estimates that change during the trading day.
Several open questions remain: What concretely triggered Friday's sell-off? Was it a single news item, a broader sector move, or a gradual reassessment? And how long will the tension between the spending plans and the revenue base last? These are questions the sources do not answer, but they will likely shape the market's assessment of Meta and other AI-heavy companies in the weeks ahead.