In early November 2026, doubts about returns on artificial intelligence investment flared again. Gary Marcus, a prominent commentator, wrote on Nov 5 that "the Generative AI bubble may finally have popped" and pointed to market turmoil. In the weeks before, he had published a string of posts questioning the real-world payoff of AI capital spending, CoreWeave's share price performance and the disclosure in Anthropic's listing filing.
The facts
In his Nov 5 post, headlined "Breaking: Mayhem in the market," Marcus said flatly: "The Generative AI bubble may finally have popped." The post offered no specific market data but drew a direct link between the turmoil and the possibility that the AI bubble has burst.
On Oct 14, Marcus cited a new study finding that it "remains 'very difficult [to find] actual, materially measurable financial impacts' from spending on AI." He described the study as "yet another study pointing in the same direction," suggesting similar conclusions had been reached before.
On Oct 13, Marcus published a post titled "Could this be the Frontier Labs' WeWork moment?" He cited "some ominous signs" and likened the position of frontier AI labs to WeWork's bubble collapse.
At the stock level, AI cloud provider CoreWeave became a focus. On Oct 22, Marcus wrote that "all the king's horses and all the king's men haven't been able to put CoreWeave back together again," noting that while nobody in the tech industry wants to see the company collapse, its stock had still fallen more than 50% over the previous six months.
Then, on Oct 26, Marcus turned to Anthropic's listing process with a post titled "What Anthropic left out of their draft S-1," warning: "Buyer, beware of omissions." The post implied that Anthropic's draft S-1 had gaps in disclosure but did not specify what was left out.
| Date | Event | Key point |
|---|---|---|
| Oct 13, 2026 | Marcus draws WeWork comparison | Says frontier AI labs show "some ominous signs" |
| Oct 14, 2026 | Marcus cites new study | AI spending hard to tie to materially measurable financial impact |
| Oct 22, 2026 | Marcus comments on CoreWeave | CoreWeave stock down more than 50% over six months |
| Oct 26, 2026 | Marcus comments on Anthropic draft S-1 | Implies incomplete disclosure, warns "buyer, beware of omissions" |
| Nov 5, 2026 | Marcus says bubble may have popped | Cites market turmoil but offers no specific data |
Analysis
Marcus's series of posts builds a multi-front challenge to the AI investment case, from macro research to individual stock performance to listing disclosure. The study he cited on Oct 14 directly questions the rationale for the current wave of large-scale AI infrastructure spending, while CoreWeave's six-month share price collapse offers a case of the market voting with its feet. The disclosure problems in Anthropic's draft S-1, though not detailed, point to information asymmetry in the primary market.
"It remains very difficult [to find] actual, materially measurable financial impacts from spending on AI." — Gary Marcus, citing research, Oct 14, 2026
Note that these doubts come largely from a single commentator, and his posts do not provide full data or methodological detail. The precise scope and severity of the market turmoil have yet to be confirmed by more data. The details of the research on AI spending's financial impact, the deeper reasons behind CoreWeave's share price fall and what exactly Anthropic's draft S-1 omitted all require further verification.
What to watch
- Details of the research on AI spending's financial impact, and whether follow-up studies of the same kind form a consensus;
- The deeper reasons for CoreWeave's share price fall and the sustainability of the AI cloud business model;
- What Anthropic's draft S-1 omitted and whether regulators open inquiries;
- The precise scope and severity of the market turmoil, and how investors' patience with returns on AI capital spending shifts.
Investors' patience with returns on AI capital spending is being tested, but the claims still need to rest on verifiable data and disclosure documents. This article does not constitute investment advice.