Reminder that Fidelity back in March gave notice that they no longer would limit the largest holdings to 5% (e.g., in FITLX). So even if you noticed, and if you wanted to control your own risk, you'd have to sell your holdings, a taxable event.

So index funds are no solution, unfortunately. They'll lose deposits if they sit on the sidelines (as people compare 8% returns to 15+%), so their incentives are not aligned with avoiding the bubble.

The perfect scam, er virus, lives well enough to spread but doesn't kill quickly.

Index funds are the only way to guarantee that you will out perform the "average" investor. Why? Because the median investor underperforms the market, hence, buy the market and you are better than median.

I feel pretty safe that if the AI stuff underperforms for whatever reason, that excess capital will flow back into boring things like Walmart. Or if AI eats the world, well, owning an index means I still have a piece of the pie.

> owning an index means I still have a piece of the pie

You're assuming within-pie transfers.

US equities in 1990's were 40% of the world market; now they are 80%. It's pretty easy to imagine them going back to 40% or less as capital moves elsewhere. But owning indexes across currencies and markets is another layer of risk.