I think this post from adliterate is one of the most important issue to face planners. It there is one thing that planners should get paid for it is ensuring that the starting point for any comms activity is the best it can be. I love the idea of planners being "problem makers" with the key role of finding the most interesting/ specific objective.
One of the most interesting piece of work I've been involved in (a podcast campaign for the Audi TT called "TT: Remastered") came out of defining an interesting business objective. Audi wanted to sell even more of the new TTs than the original. So the role of comms was to make the car feel exclusive for as long as possible (to keep it desirable) in the face of growing ubiquity. This lead us to do a extremely underground campaign with music trend setters.