The AI spending boom is becoming so large so quickly that it's hitting an important metric watched by investors: free cash flow. Amazon's trailing 12-month free cash flow recently turned negative as AI capex surged, while Meta's quarterly free cash flow stayed barely positive in the second quarter despite strong operating cash generation. Microsoft's free cash flow remains firmly positive. At the same time, aggregate free cash flow margins are projected to fall to -2.8% this year, followed by declines to -5.4% and -5.8%, respectively, in the following two years. Revenues are rapidly expanding: At the same time Google reported negative free cash flow, it reported year-on-year growth in its cloud division of 82%.