Communication: How much, how often, and to whom?

I wrote this as a discussion starter on LinkedIn and figured I might as well put it here, with a few minor edits and expansion on ideas:

With small, short-term projects involving and/or affecting a limited number of stakeholders, communication of progress and change is fairly straight-forward. If communication takes a bit of a backseat chances are you can remedy that with a quick email or phonecall. However, with large, long-term projects like a core systems replacement, communication has to be aimed at different groups with varying levels of detail and possibly at different intervals.