It looks like one of the Goldman investors leaked Facebook's earnings.
Goldman’s Leaked Memo to Rich Investors Exposes Facebook’s Actual Earnings -- Daily Intel
Goldman’s Leaked Memo to Rich Investors Exposes Facebook’s Actual Earnings -- Daily Intel
According to the document, Facebook earned $355 million in net income in the first nine months of 2010. Net earnings were a crucial detail left out of another leak, now confirmed by the document, that Facebook earned $1.2 billion in revenue during that same time period. In case you're keeping track, that means that $50 billion valuation is roughly 142 times what they earned (during those nine months).