My litmus test for what is and is not social media depends on how many people use their real name as handles, and how actively the platform promotes real names.

My litmus test for what is and is not social media depends on how many people use their real name as handles, and how actively the platform promotes real names. Facebook, nearly 100%, Twitter, less so; reddit and HN, pretty low. Real names transform the old forum/IRC chat room into social media.