Facebook sales on SecondMarket have been hovering around the $70BN range since 6 months ago (1) so there is clearly enough interest in a private market auction to place it there.
Calling this "Grossly Irresponsible" is laughable. Facebook's stated revenue and earnings are ahead of Google's pre-IPO numbers, probably enough to justify the 3x valuation (Google IPO'd at around $25BN IIRC) they will seek in their offering.
1. http://techcrunch.com/2011/01/27/facebook-shares-dip-7-in-mo...