And just to be clear, an incredibly easy ballpark valuation would be to just take the midpoints of the rev / cost growth and go 3 years out... which gives $1.3B revenue on $1.1B costs = $200M profit. A slightly high market multiple on that (18) would still be only $3.6B. And there will be dilution, selling pressure from insiders whose lockup periods will be ending, lumpiness in the numbers... I certainly would not buy LNKD valued at $8B.

But... I will say that I would be encouraged if I were a shareholder by this:

'The company' chief executive officer, Jeffrey Weiner, said in an interview that he wasn't placing much importance on how his company's stock performed on its first day. Mr. Weiner's stake in the company is now worth more than $200 million.

"To be honest with you, I didn't give a lot of thought to what the opening would be like," Mr. Weiner said. "This isn't necessarily indicative of anything. The market will do what it will do. What we are completely focused on is our long-term plans and our fundamentals, and getting that right."'

(http://online.wsj.com/article/SB1000142405274870481660457633...)