"It's taking a lot longer to go public than it has historically," notes Barry Silbert, CEO of SecondMarket. Silbert suggests that this is one of the reasons why secondary markets are a sensible "spring training" for the public markets. Although secondary trading is currently only available to a select group of wealthy "accredited investors," Silbert is hoping that a proposed financial literacy test will allow others to meet the SEC requirement.  And although large private companies like Facebook are expected to go public, Silbert remains optimistic about the secondary market business. In 2011, it "really became acceptable for founders, for employees, and even for investors to sell stock on a secondary basis," Silbert reflects. --Katie Roof