Small medieval towns and villages would likely have been populated by one or more high-density networks, and closed networks still exist in working-class and ethnic communities in modern cities. On the other hand, those towns in the Middle Ages where a middle class was forming and social mobility increasing were characterized by low-density (or 'open') networks... For our purposes here, what matters is that high-density networks act as efficient mechanisms for enforcing social obligations. An individual belonging to such a communication net depends on other members not only for symbolic exchanges but also for the exchange of goods and services. The only way to preserve one's position in a network, and hence to enjoy these rights, it to honor one's obligations, and the fact that everyone knows each other means that any violation of a group norm quickly becomes common knowledge. In short, density itself allows a network to impose normative consensus on its members.

Manuel De Landa, 'A Thousand Years of Non-Linear History'