Ian posted a meditation on the importance of media to messages today. Of course, Mr. McLuhan comes to mind (although his point was more about which of media and messages is more worthy of study than anything else). The choice of medium is an important one for any message; announcing a product with a press conference is different from announcing it with a press release, which is different from announcing it in an advertisement. Heck, this blog would be a different place if it had black text on a white background, or red rather than lime green titles. And you can alter the perception of the words 'I love you' any number of ways, depending on your choice of body language and tone of voice.
I'm tempted to see all this from an anthropological/biological perspective, to return to my constant theme of our monkey brains being way more important than we think they are. How fine is the line between being a good communicator and being manipulative? How much of that distinction is based on mastery of the parts of the message we normally call 'media'?