As it turns out, Twitter is pretty useful for academics. It's helpful a way of staying in touch with new things in my field. People use Twitter to share new discoveries and announcements about grants and conferences. By following others in my field and engaging them in conversation, I've made a few friends
But Twitter is also a good tool for learning to write. When I teach writing, I urge my students to use short words and short sentences. This seems to fly in the face of what they learn in high school, where they're taught to use ten-cent words when a one-cent word will do.
As odd as it may sound, I use Twitter and Facebook as a means of training myself to say things that matter to me in short form. James K.A. Smith says something similar in the sidebar to his Fors Clavigera blog; like me, he uses his blog to practice writing quickly and without much editing.
Twitter rewards brevity. If you can't say it quickly, you can't tweet it. And if you can't say it well, it will go unread. I can't say my tweets are great writing yet, but like any habit, the only way I can imagine changing my writing is by practice.