Former Fidelity fund manager George Noble compared the current artificial intelligence boom to a merger of the dot-com bubble and the subprime crisis, warning that massive capital deployment may not yield adequate returns for investors.

Noble made the remarks during an interview with Steve Eisman on The Real Eisman Playbook. He argued that while the technology may succeed, the financial structures supporting it are fragile. "Show me the ROI," Noble said, suggesting that funding could dry up if returns fail to justify the scale of investment.

Rising debt and market valuations

The warning coincides with a rally in AI-linked stocks. Advanced Micro Devices (NASDAQ: AMD) crossed $1 trillion in market value for the first time on Monday, driving the Nasdaq 100 to a three-month high. However, the financing burden on major tech firms is expanding.

Goldman Sachs projects that hyperscaler debt issuance will reach a record $420 billion in 2027, a 60% increase from 2026 estimates. This surge in borrowing raises concerns about sustainability if revenue growth lags behind capital expenditure.

Customer concentration risks

Steve Eisman highlighted significant concentration risks within the supply chain, particularly regarding Nvidia Corp. (NASDAQ: NVDA). Data from Nvidia’s latest quarter indicates that five direct customers account for approximately 70% of its accounts receivable. Eisman described this dependency as "very frightening."

Noble estimated that roughly 70% of hyperscaler AI revenue derives from OpenAI and Anthropic. He warned that financial trouble at these key entities could reverberate through the broader ecosystem. Eisman agreed, noting that circular financing among suppliers, customers, and investors creates systemic vulnerability.

Microsoft counters concentration narrative

Microsoft Corp. (NASDAQ: MSFT) presented data suggesting AI demand is broader than just frontier-model companies. The company reported that nearly 90% of its Microsoft Cloud revenue in fiscal 2026 came from customers outside OpenAI and Anthropic. Additionally, Microsoft’s contracted commercial revenue backlog excluding OpenAI grew 25%.

Market sentiment remains cautious but optimistic

Prediction markets currently assign a low probability to an imminent AI bust. A Polymarket contract with nearly $3 million in traded volume places the chance of an AI-industry downturn by December 31 at about 11%. Despite this, the growing web of financing links continues to fuel debate over whether the boom depends excessively on continuous capital inflows.