Mark Zuckerberg
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Facebook: Mark Zuckerberg 'Building a mission and business'

The boss of social network Facebook has spoken for the first time of the drop in his company's market value.

Mark Zuckerberg called the drop in his firm's value "disappointing". The value of its shares is almost half the $38 debut price in May.

But he says Facebook is a mission driven company "building a mission and building a business go hand-in-hand".