????上周四，在LinkedIn上市之日涌現的瘋狂買勢，令這家職業社交網站的大部分長期投資者發了一筆意外之財，尤其是網站創始人雷德?霍夫曼和其私募股權投資人。

????上周四午盤LinkedIn股價飆升115%，令霍夫曼所持股份價值從8.52億美元飆升至令人目眩的18億美元。

????但一位LinkedIn的重要投資者——高盛(Goldman Sachs)，決定遠離二級市場的狂歡。事實上這在大股東中也是絕無僅有，高盛決定在上周四LinkedIn上市當天，將所持的全部871,840股股份以IPO價格45美元/股拋出。發生了什么？

????高盛拒絕置評，看上去售罄也未帶來巨大經濟損失。高盛以IPO價格賣出三年前購入的LinkedIn 股票，總額3,400萬美元，肯定是賺錢的。2008年年中，LinkedIn曾以每股5.56美元的價格從首席技術官手中回購股票，因此高盛此次售股的每股盈利可能為39美元左右。

????但上周四LinkedIn的股價大漲說明高盛本應賺得更多。別忘了，在此類價值最大化行動中高盛往往都有出眾表現。而且，即便LinkedIn的估值存在泡沫，上周該股的火爆走勢似乎也說明泡沫短期內無破滅之虞。

????又或者是高盛認為LinkedIn可能會重蹈本月另一宗熱門IPO的覆轍，即5月4日中國社交網站人人網的首日上市之路。IPO價格為14美元/股的人人網首日開盤漲幅超過70%(見上圖)，早間更是一度突破24美元。

????但市場熱度很快下降。人人網首日收于18美元，較日內高點低25%，并且接下來連跌6個交易日，最低至12.60美元，比IPO價格還低10%。在上周四的社交網站狂歡中，人人網漲4%，但也只是略高于14美元。

????LinkedIn資本狂歡持續的時間很可能長于人人網。但拋售的理由也顯而易見，以LinkedIn最近108.55美元/股的股價計，市盈率已高達666倍。

????The LinkedIn (LNKD) buying frenzy Thursday is a windfall for most of the business networking company's longtime shareholders, led by founder Reid Hoffman and his private equity backers.

????The 115% surge in LinkedIn shares at midday Thursday sent the value of Hoffman's stake, for instance, soaring from a merely huge $852 million to a surreal $1.8 billion.

????But one sizable LinkedIn investor, Goldman Sachs (GS), decided to sit out the secondary-market fun. Practically alone among big holders of the stock, Goldman decided to dump it all in Thursday's debut, selling its entire 871,840-share stake at the IPO price of $45 a share. What gives?

????Goldman declined to comment, and it's not like the firm is taking a bath by selling out. Goldman stands to make something on the order of $34 million by selling the LinkedIn shares at the IPO price, three years after it bought the shares. In mid-2008 LinkedIn was paying $5.56 a share to buy back stock from its chief technology officer, so it stands to reason Goldman's per-share profit on this deal is around $39.

????Yet Thursday's blastoff says Goldman could have made even more. The firm's supposed to excel at this sort of value-maximizing activity, after all. And even if LinkedIn's valuation is on the bubbly side, the massive for the stock this week seems to suggest that particular bubble is in no danger of imminent collapse.

????Or is it? Goldman may be banking on a replay of this month's other hot IPO, the May 4 debut of Chinese social networking company Renren (RENN). Its shares jumped more than 70% (see chart, right) when trading started, topping out at $24 early on their first day after pricing at $14.

????But how quickly the Renren craze faded. The stock dropped 25% from its peak on opening day to close at $18, then dropped in each of the next six trading sessions before bottoming out at $12.60, 10% below the IPO price. The stock was up 4% in Thursday's social networking party but is only just above $14.

????LinkedIn mania may well last longer than Renren's run did. But it's easy enough to see the case for selling any stock that is trading, as LinkedIn is at a recent $108.55, at 666 times earnings.