Back in the day, real-time communications were rare. Only when you were face to face with someone could you conduct a synchronous conversation. Other than that, communications were pretty send-and-wait in nature: send the messenger and wait for his return (and hope he doesn't get killed), send the letter and wait for the response. News traveled slowly either by "pass it on", troubadours, or town crier. Information could only move as fast as the people who bore it. Some early technologies (smoke signals, semaphore, etc.) closed that gap by providing point-to-point communication over a distance. However, these technologies still required humans (preferably with eyes) to receive the information and then disseminate it.
The first great information revolution was movable type (well, I guess language is actually first. And an argument can be made that the cave paintings at Lascaux are still telling us things tens of thousands of years later.). But, movable type provided the ability to know with a reasonable amount of certainty that you message was being delivered with a relatively high degree of fidelity to the reader. This overcame the issues presented by the "telephone game" nature of pass-it-on communications. Television is a logical extension of this, as is Web 1.0.
Telegraph followed suit allowing geographically distinct participants communicate in near-real-time. Telephone picked up where telegraph left off and video conferencing tries to take it one step further.
In fact, the promise of technology up through the 20th century was to provide synchronous person-to-person (or person-to-persons), rather than point-to-point, communication. The great irony is that, now that I have it - I can specify any similarly equipped colleague in the world and have a television-like resolution conversation with them - I almost never use it. The fact is that unless a conversation is focused on coming to a resolution or concensus, I don't need full duplex presence. For process-oriented communication or communication for the sake of disseminating content, asynchronous communication is actually preferable.
In fact, the great majority of my information consumption is an exercise in time-shifting and queue management. I can fire off an instant message and know that when I get back from getting coffee, the response will likely be waiting for me. I just got caught up on the current season of "Lost" because I used Tivo to time-shift and queue the watching of the episodes until tonight. More often than not, I let calls to my mobile fall into voicemail and, more often than not, my response is directed into that person's voicemail.
So, feel free to shoot me an email, SMS, or IM regarding this topic. I'll get back to you as soon as my queue clears...