I suppose a simple story of the last 3 bubbles is the first one was a bet on stupid companies but it at least left a bunch of useful internet infrastructure and related technology in its wake, the second was a bet on stupid financial derivatives but left a bunch of houses in its wake, the 3rd was a bet on reinventing the bus with a bus, "uber, but for" for everything, and then finally on magic beans.
I guess maybe there are a bunch of cheap used graphics cards now.
Hopefully the bust of the 3rd one isn't as consequential as that of the 2nd, at least, but we really need to consider once again whether our system of allocating capital efficiently - capitalism - does what it is supposed to be.