They are multi-level and lumpy. Although we tend to think of computer networks as horizontal webs, they, too, seem to naturally develop in clusters. While the long first generation of mail systems sought to serve captive audiences of one network, the new generation is quickly moving to use gateways between networks. People have worked in small groups for millions of years. Computers can support this natural way of working, or, perhaps unintentionally, fragment it.
Online proximity is profoundly different from physical proximity.
For better or worse, online everyone can be an equally short distance from everyone else. Whether in one site or many, what we have in any large group is a network of co-located small groups. Whether in one site or many, any large group can benefit from network approaches to its work.