As Enterprise Social Networks become the ‘killer app’ for unlocking tacit information and enabling connections within organisations, there can be a tendency to take an organic approach to the relationships and networks that will emerge.  However, this 2007 (!) article from McKinsey & Company, describes the underlying structures of informal networks. Authored by Lowell Bryan, Eric Matson and Leigh Weiss, it is an essential foundation read for communicators and technologists striving to foster networks on their collaboration platforms, whether they be Yammer, Jive, Connections or other.

Harnessing the power of informal employee networks | McKinsey & Company.

Just as formal hierarchical structures define management roles, formal network structures define collaborative professional ones. In this way such networks can enable large companies to overcome the problems of very large numbers by creating small, focused communities of interest integrated within larger, more wide-ranging communities—for instance, subcommunities focused on different aspects of financial services, such as wholesale and retail banking.