One of the first documents that gets pulled out whenever a change is being contemplated is the organization chart. The sheet of boxes and lines supposedly shows where everyone fits in the organization and who they take orders from.
Except it doesn't really.
It doesn't highlight the old-timer that people look to whenever management makes an announcement to get a sense of whether to take it seriously. And it doesn't show how the executive assistant gives his favorites a heads-up on the downsizing that's coming in a few weeks so they can better position themselves.
Managers react in one of two ways at the first signs of the hidden social network. Some get angry and try to force the "official" structure on staff. Better are those who embrace it, identify the key players in this hidden network, and work to win them over.