Goldman Sachs stirred up some heated opinions on the Web last month when it invested in Facebook at a $50 billion valuation. I argued here that the valuation shouldn't have shocked everyone as much as it did because the social network had been trading at that price on the secondary market for a while. But now it's soared far past that point. In a weekly update posted late last night on TechCrunch, MG Siegler noted that Facebook's stock is now trading at more than $28 a share. With roughly 2.5 billion shares outstanding, that price point pushes the valuation of the company north of $70 billion.

And we're back again with our now weekly update on the insanity surrounding Facebook's stock in the SecondMarket auctions. Last week, the stock saw the beginning of a rally back to $27 a share, good for a $67.5 billion valuation (based on roughly 2.5 billion shares outstanding). This week, the good times continued to roll. Facebook's stock hit $28 a share, to push the valuation of the company back to a cool $70 billion or so.

This is still slightly off the record high of $28.26 a share (a $70.65 billion valuation) set in mid January, but it's clear that Facebook's stock is storming ahead once again, and quickly. This was the 11th auction SecondMarket has done on the stock.

Do I hear $75 billion next week?

Read the full story at TechCrunch.