What does a Program Manager do?

Yesterday and today I am in training called "Engineering Excellence for New Program Managers".  It has been very informative so far.

It was interesting that we spent almost the entire first day talking about the PM job description.  One of the hardest things for a new PM to figure out (at least at Microsoft) is "What are my responsibilities?".  The instructor put up a slide with a bunch of different shapes on it.  The shapes had different labels: "Development", "Localization", "Test", "User Experience", etc.  Next, he told us the responsibilities of each of these groups.  Significantly, Program Management was not one of the the shapes.

Then came the punchline: Program Management was the white space around all the shapes, and management of that area was our responsibility.  Our job is to make sure that all the other groups work together and move forward on our projects, and we are ultimately responsible for getting the project done.

I thought this was a very interesting illustration.  Any observations?