LLMs are reshaping how marketplaces operate, presenting both challenges and opportunities. The core issue, referred to as the DoorDash Problem, arises when AI interfaces like ChatGPT become the primary way customers search for services, potentially cutting marketplaces out of the transaction loop. As LLMs streamline customer interactions, marketplaces could face higher acquisition costs and a loss of customer engagement avenues, such as ads and upselling. Three critical factors determine how vulnerable a marketplace is to LLMs: the difficulty of supply aggregation, the degree of marketplace management, and the nature of customer engagement. For instance, aggregating hotels is easier than individual home rentals due to the standardized nature of hotels versus the unique offerings of Airbnb hosts. Marketplaces that manage customer interactions extensively—such as ensuring quality and handling transactions—are better positioned to withstand LLM competition. DoorDash exemplifies a marketplace that, despite the threat, maintains a strong customer reliance on its delivery and service quality, which LLMs are unlikely to replicate fully. The article also categorizes marketplaces by their transaction frequency and purchase consideration. High-frequency, low-consideration marketplaces like ride-sharing services tend to retain customers better than low-frequency, high-consideration ones like travel planning. As LLMs become more integrated into the search process, marketplaces reliant on search traffic, like Expedia and TripAdvisor, may see their economic models upended, while e-commerce giants like Amazon benefit from their high level of management and customer engagement. Ultimately, the impact of LLMs will vary widely across different industries, with some marketplaces needing to adapt significantly to survive.