The age of privacy is over,says Mark Zuckerberg, the founder of Facebook. People have become more relaxed, he says,about sharing information with people they don't know. Facebook has over 500 million users - more than the population of the United State. According to Zackerberg, Facebook is just helping people to communicate. But some people think this explosion of social network services is a dangerous development. Professor Sherry Turkle's latest book,Alone Together,claims our obsession with Facebook is making us 'less human