We've been having some very interesting chats with our Clients about Henry Jenkins's concept of the "Transmedia Narrative" and how this relates to marketing. You can see my thoughts on the subject in this recent article in Campaign.
Much has already been said on the subject of "Transmedia Planning" e.g. this from Faris plus this and this from Henry Jenkins. The below diagram is from Faris's post.

I'd like to propose an addition to this thinking. And perhaps it's something that was already implicit in Faris's version. Although the disparate channels don't have to be saying the same thing, there needs to be some redundancy between them so that people can bring the parts together to form a coherent story. There needs to be a strong core theme.

Now this is hardly revolutionary. However, it feels a valuable addition to the story. Besides, it makes the diagram look more like a ship's wheel (is that the right term?). Which has got to be a good thing.
If you're interested in reading more about the transmedia narrative then you must read Henry Jenkins's recent "seven principals" (part 1, part 2) in addition to chapter 3 of "Convergence Culture".