We've been tracking these fabulous SecondMarket Facebook stock auctions for the last three weeks. The shares hit a roughly $50 billion valuation in a big auction in late November, when $40 million changed hands. Last week the price edged up 1.2% to $21.01. This week's auction has now closed as well. The closing price was $21.90, up 4.2% from last week. Someone actually guessed that price in our TechCrunch tshirt contest (see comments), and we'll be contacting them and shipping it out right away. What will next week's price be? Be right and get a TechCrunch Tshirt.