The Bank of International Settlements sums up the AI bubble concerns pretty well.

the optimism surrounding AI may not last, despite its promise of future productivity gains. The current surge in capital expenditure could prove unsustainable if supply bottlenecks restrain production. Intense competition for market leadership may fuel overinvestment further, as seen in previous innovation waves, increasing the risk of a sharp reversal if AI payoffs disappoint.

The positive economics effects we have seen from AI so far may be mostly due to economic stimulus effects. Spend a massive amount on construction, whether of public infrastructure with public dollars or private capital with private dollars, and you get a big multiplier effect. This raises growth and potentially also inflation. Productivity gains from AI are expected by most people/experts, but the question is really the timing. If they obviously show up while hype is still high, the train rolls on. If they show up on a lag of years or decades, the bubble bursts and there is a significant period of pain before things gradually and hopefully permanently pick up again. This doesn’t matter to the wealthy and immortal among us, but to those of us in our last decade or so of work before retirement, it’s our lives!

I also wonder how long-lived these capital goods are. Public infrastructure operates for decades even if it gets somewhat obsolete compared to the latest and greatest new designs, but computer hardware evolves so fast I wonder if these massive data center buildings and their appurtenances are going to be operable a decade from now.