The document discusses the rationale behind Quora's decision to build their own machine learning (ML) platform instead of buying commercial solutions, highlighting seven key reasons including the need for integration, scalability, and control over ML processes. It emphasizes the blurred lines between ML and product development, the advantages of open-source technology, and the strategic importance of ML as a core competency for Quora. Ultimately, it concludes that a sustainable ML platform is essential for driving innovation at scale.