Check the link below for some Facebook alumni club details
These ex-Facebookers are leaving before any I.P.O. of the company’s shares. They can do that because Facebook shares are surprisingly liquid. The rise of exchanges like Second Market and SharesPost over the last couple of years have allowed shareholders in private companies to sell their stakes more easily than before. These markets function much like a stock exchanges for publicly traded companies, although the pool of buyers and sellers is much smaller. Facebook’s overall value is around $30 billion on the exchanges.