Prior to the Web, we had hundreds of years of experience with broadcast media, from printing presses to radio and TV. Prior to email, we had hundreds of years experience with personal media — the telegraph, the telephone. But outside the internet, we had almost nothing that supported conversation among many people at once. Conference calling was the best it got — cumbersome, expensive, real-time only, and useless for large groups. The social tools of the internet, lightweight though most of them are, have a kind of fluidity and ease of use that the conference call never attained: compare the effortlessness of CC:ing half a dozen friend to decide on a movie, versus trying to set up a conference call to accomplish the same task.
The radical change was de-coupling groups in space and time. To get a conversation going around a conference table or campfire, you need to gather everyone in the same place at the same moment. By undoing those restrictions, the internet has ushered in a host of new social patterns, from the mailing list to the chat room to the weblog.