Ben Thompson:

But the reasons functional organizations are theoretically “best” are the exact same reasons why it is so difficult to manage a functional organization. Get any of the following wrong and your organization – e.g. Microsoft – is in a far worse place than if you had settled for a “good enough” divisional structure.

Great insight that applies not just to organizational structure, but to nearly anything. It’s better to be “good enough” than not quite “great”.