> I think the correct term here is “speculative bubble”, but there are deep similarities between a speculative bubble and a Ponzi scheme.
There are deep differences, too, most obviously the one highlighted by the “scheme” in ponzi scheme.
> In both a speculative bubble and a Ponzi scheme, early investors are paid out with funds taken from later investors, for an asset which does not have enough utility to justify those payouts.
In a ponzi scheme, money is deliberately directed to early entrants to cover the conscious absence of any mechanism to produce actual value.
That's not true of speculative bubble; yes, the usual market mechanisms involve movers out of market get money from those moving in, but outside of fraud (which can make usual market action ponzi-like) its not conscious cover for an absence of a return-generating mechanism. Yes, a ponzi-operator produces deliberately a conditions similar to that which is retrospectively observed when the market misperceives value for a time, but that's the same as saying fatal accidents produce the same results as murder plots. We call them different things for good reason, and it is worth distinguishing them.
> And I don’t think the bad faith component of Ponzi schemes should be considered a necessary component.
Someone having advance and certain knowledge of the absence of return mechanism is quite relevant and distinct from a market misperception, especially when looking at a prospective bubble that hasn’t popped (so its the differences between “there is specific concrete evidence someone engineered this fraudulently” and “my perception of the future differs from the consensus”.)
Redefining terms so you can use terms that communicate greater certainty and have higher emotional valence than is warranted by what you are actually describing is bad, in much the same way as an (actual, proper definition) ponzi is bad. Its an attempt to mislead and motivate action based on misleading people.