The price of Facebook stock has jumped as much as 42% in the past four months. Membership is topping 300 million users to take Facebook into profit for the first time.
SecondMarket is among services that allow Facebook employees to sell shares, but the company is expected to sell stock through an initial public offering (IPO) in the next 12 to 18 months.
A Facebook IPO may attract the same high level of attention as Google's share sale in 2004, according to analysts.
A $200 million investment in Facebook by Russia's Digital Sky Technologies in May, which valued Facebook at $10bn, is also boosting expectations of an IPO.
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