Computer mediated communication (CMC) appeals to a certain group of people and turns off others. Introverts and reflective thinkers love it. Extroverts and "on ones feet" thinkers do not generally like it. People who become energized on the give and take of conversation often feel that something is lacking. They point to the classical examples of great speakers, as an example of what discussion should be – face to face, without the deadening, distancing effects of the Internet.
Yet, oratory, except for the very privileged audience that is present physically, was and is often mediated. Even in classic Rome, an orator's words had to be repeated by other people (either synchronously or asynchronously) for him to have much impact beyond the immediate audience. The more famous and effective orators made better use of stylistic devices to make their words memorable (like a catchy tune sticks with you), worthy of recording (in an era when writing was very precious), or worthy of action. They also (giving a nod to Vygotsky here) made good use of their understanding of their own culture - using certain words or images important to their culture - to further their impact.
Winston Churchill and others made great use of the radio to spread their message. Martin Luther King, Jr. (and John F. Kennedy) actually made great use of the television as well as the local audience to get beyond their immediate locale in order to have a national impact. If they had been limited to speaking only to those people who were present - and could hear them without a microphone! Surely, they would have still been great, but how far could their message have spread without word of mouth, papers, radio, and television? As well as the very situational frame for each person's message - based in the needs of the culture and in its meaningful words and images.
What will the best use of digital media be in communication in general and education in particular? It is hard to say. Now, we have been recreating what we know in a new venue - which we always have done badly. Shortly, we will start to see what it can do well. I am reading Ian Bogost's book Persuasive Games, which is actually all about the new procedural persuasion possible in virtual worlds and digital games. We are just getting started with figuring out where we should use the new technologies for greatest value.