Enthusiasm always runs ahead of reality during financial bubbles. Truths are stretched as fantasy takes flight. Envy, overconfidence, greed and the rush of gambling kindle a herd mentality.This cycle is well along for artificial intelligence (AI). Caution lights are flashing as equity valuations run far ahead of cash flows. At this point, an impresario usually insists that “this time is different”. These days it’s Amazon founder Jeff Bezos. It’s a “good” kind of bubble, he argues. “When the...