The document discusses the evolution of digital media buying over the past 15 years. It describes how buyers have gone from manually purchasing sites to now having millions of sites to choose from. This has increased reliance on networks but reduced visibility. New platforms like exchanges and demand side platforms are bringing more transparency around pricing, granularity in purchasing impressions, and control and insights for buyers. However, change is difficult and old habits die hard. Ultimately, specialization, centralization of buying technology, and leveraging data will be required for success in the future of digital media buying.