I think one of the most interesting observations here is that the informal structures described always exist in an organization regardless of the formal structures. The formal structures should exist to hold explicit power and keep informal power in check but that's not to say that informal power isn't still at play.

> The rules of decision-making must be open and available to everyone, and this can happen only if they are formalized. This is not to say that formalization of a structure of a group will destroy the informal structure. It usually doesn't. But it does hinder the informal structure from having predominant control and make available some means of attacking it if the people involved are not at least responsible to the needs of the group at large.

I've found that understanding how informal power works in an organization is extremely important if you really want to get something done - especially if that organization has dysfunctional formal structures.

This article is the best description of the nature of those informal structures that I've ever seen.