Microsoft CEO Satya Nadella Fortune via Reuters Connect A version of this story originally appeared in the BI Tech Memo newsletter. Sign up for the weekly BI Tech Memo newsletter here. For several years, Big Tech has operated under a simple rule: spend more on AI, or investors will assume you're falling behind. This earnings season, that rule may have changed. Even a year ago, if one of the cloud giants had merely held its AI spending plans steady while rivals kept increasing theirs, Wall S...