Very soon, Facebook will go public. That means anyone will be able to buy shares of the social networking giant on the Nasdaq exchange. But sophisticated investors have already been buying pieces of Facebook and many other hot tech stocks, on private exchanges....And now it seems that trading in private company shares is poised to grow, thanks to recent changes in the law.

http://www.wbur.org/npr/152015043/before-the-ipo-a-private-market-for-tech-shares