The SecondMarket Facebook shares auctions are back on after a holiday break, and the valuation is up big time. The last auction prior to this one closed December 15 at $22.75/share. Today it hit $28.26 per share. With 2. 5 billion or so shares outstanding, that’s a $70.65 billionish valuation. A month and a half ago shares were trading on SecondMarket at a $50 billion valuation.