This BoingBoing post has an excellent explanation of why being in the same room with someone has so many more possibilities for interaction than talking on the phone or emailing. I've written about this before, but the first half of pspinrad's post really makes a convincing case.
Here's my theory: communication layers itself within the available bandwidth. There is always a surface meaning, the main content of the communication. In a presentation, for example, it's the speaker's words and slides. These are what the meeting is "about". But below that, the audience and presenter engage in a back-and-forth of engagement and disengagement, understanding and disagreement/not understanding, etc - all without words. At a concert, a rock band plays songs ("about"), but below that, they're standing still or active, looking the audience in the eye or staring at their gear, the audience is dancing or getting beers, et cetera.
I suspect, though, that communication always finds a way to pack some extra layers into the available bandwidth. The lowest-bandwidth form of communication I can think of is texting. You get about 100 characters which can be letters, numbers, or symbols. It's physically difficult and technologically unreliable. Yet beneath the words (or abbreviations), any given user might mean something different, or something additional, when they use punctuation as opposed to when they don't. I know I do, and I don't even text all that much.
So there's a theory, and a counterargument to go along with it. I can be frustrating that way.