"You have one identity," he emphasized three times in a single interview with David Kirkpatrick in his book, "The Facebook Effect." "The days of you having a different image for your work friends or co-workers and for the other people you know are probably coming to an end pretty quickly." He adds: "Having two identities for yourself is an example of a lack of integrity."
source: http://venturebeat.com/2010/05/13/zuckerberg-privacy/