Doordash's stock plummeted 17% for its worst session ever as investors rejected the company's aggressive spending strategy.The food delivery platform said it plans to shell out "several hundred million dollars" next year on new product initiatives like autonomous delivery and a new global tech stack.These plans will improve its product globally, but involve "direct and opportunity costs" in the short run, Doordash said.CEO Tony Xu defended the company's spending decisions during the earnings cal...