All good things must come to an end, and so it is withSecondMarket Inc.'s four-year run as the biggest private market forbuyers and sellers of Facebook Inc. shares.

The initial public offering Facebook has planned for todayforced an end to the private trading, which has driven thecompany's valuation up more than 10-fold since 2008 to exceed $100billion. Commissions on Facebook trading may have accounted foralmost a third of SecondMarket's revenue last year.

The challenge to replace those sales has forced SecondMarketChief Executive Officer Barry Silbert, 36, to turn to even moreexotic investment opportunities to retain his 100,000 wealthyindividuals and institutions: wine, fine art, diamonds,intellectual property and other so-called alternative assets.