Is Privacy an Anomaly on Social Networks?

Google's chief internet evangelist, Vint Cerf, suggests that privacy--at least in the context of social networks--might be an anomaly. 

That is not a blanket statement about government data collection or privacy in some other contexts, only a recognition that the whole point of social networks is sharing. 

As was true for most people in prior historical periods where most people lived in small villages, and where "everybody knew everything" about other people in the community, something of that same process affects online social networks as well.