Who are the best writers on Twitter?

Brevity is the soul of wit and the essence of Twitter, but it's a challenge to write well in such brief bursts. Who does it best? Mallary Jean Tenore has some nominees on Poynter: "Twitter is a powerful tool for writers. With its 140-character limit, it’s like an electronic editor that forces us to find a focus and make every word count. It’s a verbose writer’s friend and worst enemy — a constant reminder that it’s often harder to write short than it is to write long."