"Online social-networking tools ought to be great at fostering small, connected, passionate groups of people. Twitter and Facebook are 'conversational media.' But when the conversation gets big enough, it shuts down. Not only do audiences feel estranged, the participants also start self-censoring.

"At a few hundred or a few thousand participants, you're having fun--but any bigger and it falls apart. Social media stops being social. It's no longer a bantering process of thinking and living out loud."