People often assume that "peer-to-peer" or "distributed" always means decentralized. But it doesn't. While successful systems like Gnutella and Freenet take decentralization as a primary design goal, others like distributed computing companies are largely centralized. And most current peer-to-peer architectures are somewhere in-between: whether a hybrid approach like Napster, a hierarchical system like DNS and NTP, or a complex system such as Groove.

Nelson talks about centralization and decentralization as a basic design principle, relying heavily on examples from current systems. He illustrates the four fundamental patterns of building distributed systems (pure client/server, ring, hierarchy, and pure decentralization). These approaches have different benefits and drawbacks, including scalability, manageability, complexity, security, and resistance to legal or political intervention.

Nelson concludes with an in-depth exploration of two systems he designed with similar goals. One system, Hive, was fully decentralized. The other, Popular Power, was fully centralized. Each approach has advantages, disadvantages, and lessons to learn. In the end, while decentralization offers exciting flexibility and scalability, centralized systems are often easier to build, manage, and understand.