This doesn't really apply to what we all do, but I found this recent article appearing in The New York Times very interesting, and demonstrative of the fundamental shifts taking place in how people communicate.
According to the story, the once-indispensable tool for busy offices and households, voicemail, appears to be going the way of the dodo. Compared to text messaging, which has increased more than tenfold over the last three years, voice mail is slow and cumbersome. As a result, fewer people are using it, and when they do, they are taking longer to check their messages.
Because people generally read at least twice as quickly as they can speak, and text messages require no log-ins or waiting, it's estimated that text messaging is about 15-20 times faster than voice mail for recipients. Text messages also tend to be more efficient because the people sending them get to the point more quickly.
So, ultimately, text messaging does a better job of respecting people's time. Something to think about.