Ben Abraham (Critical Distance)
An Australian academic, Ben Abraham is the person you follow while making sure to follow everyone he talks to. When you feel the tremors of intellectual conversation, the best thing you can do is open Ben's tweets.
You'll learn, especially if you reply with contrarian thoughts -- he'll open your mind to alternative opinions and consider your input attentively. He's a smart guy, a real thinker, and the sort of Twitter person that's worth following for more reasons than a desire to waste time online.