A paraphrase from the late, great, Eberhardt Rechtin:
"Most architectures are the products of deliberate and centrally controlled development efforts. There was an identifiable client or customer (singular or plural), clearly identifiable builders, and users. The role of the architect existed, even if it was hard to trace to a particular individual or organization. The system was the result of a deliberate value judgment by the client and existed under the control of the client.
However , many systems are not under central control, either in their conception, their development, or their operation. The Internet is the canonical example, but many others exist, including electrical power systems, multinational defense systems, joint military operations, and intelligent transportation systems. These systems are all collaborative in the sense that they are assembled and operate through the voluntary choices of the participants, not through the dictates of an individual client. These systems are built and operated only through a collaborative process."
"In a collaborative system, the greatest leverage in system architecting is at the interfaces. The greatest dangers are also at the interfaces. When the components of a system are highly independent, operationally and managerially, the architecture of the system IS the interfaces. The architect is trying to create emergent capability. The emergent capability is the whole point of the system; but, the architect may only be able to influence the interfaces among the nearly independent parts. The components are outside the scope of and control of the architect of the whole."
"Virtual collaborative systems lack both a central management authority and centrally agreed-upon purposes. Large-scale behavior emerges, and may be desirable, but the overall system must rely upon relatively invisable mechanisms to maintain it."
"The Web is even more [of a distributed collaborative system] than the Internet in that no agency ever exerted direct central control, except at the earliest stages. Control has been exerted only through the publication of standards for resource naming, navigation, and document structure. Although essentially just by social agreement, major decisions about Web architecture filter through very few people. Web sites choose to obey the standards or not, at their own discretion. The system is controlled by the forces that make cooperation and compliance to the core standards desirable. The standards do not evolve in a controlled way, rather they emerge from the market success of various innovators. Moreover the purposes the system fulfills are dynamic and change at the whim of the users."
"A collaboration is a network good; the more of it there is the better. Minimize entrance costs and provide clear conformance criteria."