Two of Nvidia's biggest customers might be turning into its biggest threat. For three years, Nvidia's stock has defied gravity on the premise that the AI industry needs its chips. On Wednesday, when Google and Amazon reported their Q1 earnings, both signaled ambitions to sell their own custom AI chips directly to customers. So far, Google's TPUs and Amazon's Trainium chips have only been available through Google and Amazon's cloud services. Customers can pay to use them, but they don't own them.