I came across this link today thanks to my friend Andrew Sullivan. In it, a college student expresses how she feels awkward speaking on the phone and thus prefers texting. The comments and quotes around it express how this phenomenon is a sign of our times, etc. - and it is, but I have to think that the true sign of our times isn't the phenomenon itself, only the form of its expression.
Communication is learned. Ever since humans started this whole language thing, it has been a learned behavior. It doesn't matter whether you believe in Universal Grammar or not (which I really don't; see my recent post) - the specific form a language takes, and the way it associates sounds (or gestures!) with meaning and action and social forms is learned. Not only that, but not every person learns it to the same degree, even among native speakers. There have always been those people who have more difficulty with language, and with specific forms of its use.
When I was doing my Masters in Linguistics, I did a small study about how children learned to talk on the telephone. This involved doing some recordings of friends' children (at the time I had none of my own) and taking a look at the patterns of their speech. It quickly became clear to me that telephone talk is managed differently from face-to-face talk, and while the ability to speak well face to face will correlate with better telephone talk, the two are not the same. Children will develop their telephone talk at a similar rate to their regular talk, but appear to be delayed in it because of the increased demands of the telephone as a means of communication. Over the telephone, you have to adjust for the fact that even though you can see everything in front of you, the person you're talking to cannot. This is actually quite a tricky basic concept, and because children learn to speak on the phone very early, you can actually watch them trying to learn it.
Letter writing involves a lack of context, and people have studied to learn how to do that for a very long time (at a later age than they would learn speaking on the telephone, because they need to know how to write). If you compare letter writing to texting, the desire to compress the length of a text message operates against any need for eloquence that might be cultivated in the longer, letter form. Yes, in texting there is the assumption of lack of visual context, but this assumption is precisely the same one that exists for letter writing and for other writing contexts such as writing for a homework assignment. Texting may appear to be easier to learn simply because by the time we're doing it, some of its base assumptions have already been learned and are well established.
Both face to face communication and telephone communication involve a very fast real-time response, while texting and letter writing do not. When people don't feel comfortable with these speed demands, and the risks that accompany an instant response to something that might be misunderstood, they'll typically choose the written format of communication. In this context, Twitter would more closely resemble texting, while instant messaging would fall somewhere in between the telephone and the text message.
Overall, I think that we need to realize that we learn all these methods of communication through practice, and we need to cultivate those skills that will be needed for our success, both socially and in our work lives. As the medium of communication changes, we adjust our behavior and learn what's next - but the underlying principles don't change as much as we might think.