Calling something a bubble can make it sound as though the underlying thing is fake. That is not really what a financial bubble means.

Strictly speaking, economists generally use the term for a situation where the price of an asset moves beyond what its underlying fundamentals can reasonably justify. Bubbles can become self-reinforcing: rising prices attract investment, that investment creates further growth and confidence, and the apparent success encourages even more money to enter. Eventually the fundamentals have to catch up with the expectations. If they don't, the process can reverse. 

With AI, we are using the word slightly more broadly. The concern is not simply that a handful of AI shares are expensive. It is that valuations, infrastructure spending and business plans across an entire industry increasingly depend on very optimistic assumptions about how much AI customers will eventually consume and how much they will be prepared to pay for it.

That distinction matters because a technology can be genuinely transformative and still have a financial bubble built around it.

AI could follow a similar pattern.

Microsoft said in July that its calendar-year 2026 capital expenditure expectation was around $175 billion after an accounting-related lease change. It spent $41 billion in its latest quarter alone, with roughly two-thirds going towards relatively short-lived assets such as CPUs and GPUs. Amazon has said it expects to invest about $200 billion across the business in 2026, while its latest results said the large increase in property and equipment purchases primarily reflected AI investment. Meta expects capital expenditure of between $130 billion and $145 billion this year. 

And to be fair, there is real demand behind it. AWS revenue grew 37% year-on-year in Amazon's latest quarter, Microsoft said Azure revenue grew 43%, and Microsoft 365 Copilot has passed 30 million paid seats. This is one reason we don't buy the argument that AI is simply a fad waiting to disappear. 

There is also an unusual dynamic inside the AI economy. The companies building the infrastructure are not always simply selling computing power to independent customers. They are also investors and strategic partners in some of the AI companies consuming huge quantities of that infrastructure. Microsoft's financial results, for example, now separately discuss the effects of its OpenAI investment, while Amazon's latest quarter included a very large accounting gain from its investments in Anthropic. 

The argument in Ed Zitron's recent piece about an "AI demand bubble" takes this much further, arguing that the industry is dangerously dependent on a relatively small number of heavily funded AI labs buying enormous amounts of computing capacity. We wouldn't treat the analyst estimates used to make that case as established fact, particularly because the cloud companies do not disclose enough detail to verify them. But the broader question it raises is a sensible one: where does the money eventually come from once you follow the chain all the way back to the end customer?

A recent NBER study surveyed nearly 6,000 senior executives across the UK, US, Germany and Australia. It found that 69% of firms were already using AI in some form. But 89% of executives said AI had made no measurable difference to labour productivity at their business over the previous three years. Among the minority reporting an impact, the researchers estimated the average productivity increase across all firms at just 0.29%. Executives expect substantially larger benefits in the years ahead, which may turn out to be correct, but that gap between what AI has delivered so far and what businesses expect it to deliver next is exactly where the financial risk sits. 

We don't think there will necessarily be a morning where everybody collectively decides AI was a mistake.

A more believable version is much less dramatic. Growth remains strong, but not quite as strong as investors expected. Businesses become more selective about the AI tools they pay for. A few heavily funded AI companies struggle to justify another enormous funding round. Some data-centre projects are delayed. Investors start demanding profits rather than promises of future scale.

Once expectations change, the same feedback loop that helped inflate the market can begin to work in reverse.

Private AI businesses that could previously raise money based on what they might become in five years suddenly have to explain how they make money today. Dozens of companies selling broadly similar AI products consolidate or disappear. Features that once commanded a £20 or £30 monthly add-on get bundled into existing software. Model providers compete harder on price, pushing the underlying technology towards becoming a commodity.

So a burst may look less like AI suddenly disappearing and more like a fairly brutal repricing of who actually captures value from it.

There would still be GPUs running, data centres operating and businesses using AI. There would simply be fewer companies able to justify enormous valuations on the assumption that they will eventually own a large part of the market.

The lesson of the dot-com bubble isn't "new technology gets overhyped and fails".

It is almost the opposite.

The internet really did transform commerce, communication, entertainment and almost everything else. But being correct about the importance of the internet did not automatically make investors correct about which businesses would win, how quickly the opportunity would develop or what those businesses were worth in 1999.

That is the comparison we think makes sense for AI.

It is completely possible that today's AI boom is simultaneously producing one of the most important technologies of our generation and a spectacular amount of bad investment.

In fact, those two things often go together. A genuinely important technological shift makes an especially convincing investment story because there is something real underneath the hype. Nobody has to invent the potential of AI. You only have to exaggerate how quickly that potential turns into revenue, or assume that your particular company will be one of the businesses collecting it.