The four words that precede every crash: “This time is different.” Except this time, the person warning about a bubble is Sam Altman, the CEO most responsible for creating it. When OpenAI’s chief executive warned last week that investors were “overexcited” about AI, markets reacted immediately. Nvidia fell 3.5%, Palantir dropped nearly 10%, and the selloff spread globally. The warning came amid a cascade of seemingly supporting data. That same week, MIT researchers published findings that 95% of...