One of the reasons LinkedIn's share price jumped so high from its IPO price of $45 was because of a very low float. There are too few LinkedIn shares trading on the public market. It is not that easy to get your hands on LinkedIn shares right now, even if you are willing to pay market price. This artificially raises the stock price.

I believe 7 million shares were floated out of ~94 million outstanding shares. If more shares are floated, the price per share should go down (not considering other factors) as there will be a larger supply of shares in the public market. The assessment that the investment banks that the IPO should be priced at $45 sounds more reasonable had all 94 million shares been floated (speaking hypothetically; this never actually happens).

For this reason, valuing LinkedIn by multiplying 94 million (total outstanding shares) by the current stock price on the NYSE (as most news articles have been doing) is probably not a very accurate measure.