"A medium's early adopters are really the most likely to have interesting things to say? How can the two possibly be correlated?"
Since you are asking for a possible explanation, and not a provable one:
People with lots of good things to say naturally seek out places where what they say is not drowned out by meaningless noise. This means that whenever a new publishing medium is established, they jump on it in order to say their good things before Zynga figures out how to use it to broadcast pleas for help milking virtual cows or whatever.
Since you are asking for a possible explanation, and not a provable one:
People with lots of good things to say naturally seek out places where what they say is not drowned out by meaningless noise. This means that whenever a new publishing medium is established, they jump on it in order to say their good things before Zynga figures out how to use it to broadcast pleas for help milking virtual cows or whatever.