Alphabet stock plunges 12.6% in worst day since 2004 IPO on AI spending doubts

Alphabet's 12.6% single-day decline erased $500 billion in market value as investors reassess the trade-off between massive AI capital spending ($51.4 billion in Q3 alone, with $195–$205 billion projected for 2026) and near-term profitability. Q3 results revealed negative free cash flow of $9.1 billion, advertising revenue below expectations, and operating profit down 25%, while AI-driven search summaries reduced ad visibility and click-through rates. This reflects a broader investor concern across Big Tech about whether AI infrastructure outlays will generate sufficient revenue growth to justify spending scale. Immediate effects include valuation pressure on Alphabet and increased scrutiny of AI capital allocation strategies across peers (Microsoft flat on earnings; Amazon down 6% after reporting $42 billion negative cash flow).