Walk into most media, creative, PR or strategy agencies and somewhere on a whiteboard you'll find a derivation of this diagram:
The diagram makes sense and certainly has relevance, but perhaps a more effective way of illustrating the concept of '360 Degree Marketing' is to draw one of these on the whiteboard:
In my humble opinion, Nike embodies [and has done so for many years] the true spirit of 360. Sometimes a swoosh says a thousand words.
[Update 4/13: Check out this post on PSFK.com. Not 100% related to this topic but a pretty interesting thought on Nike]