Stanford psychology professor Stanley Milgram once posited any two people were connected via six degrees of separation. A new quantitative study now shows most Twitter users are connected via four degrees, but with a twist. Twitter relationships have a short graph diameter and low reciprocity, unlike all previously-known human social networks. In addition a non-power-law follower distribution anomaly makes some supernodes very efficient for distributing news, as the pictured retweet tree illustrates.
