TradeVibes tried this many years ago (their assets were ultimately acquired by VentureBeat) so as a side project for fun, maybe. As a viable business, not so much.

The problems with this type of "exchange" are as follows:

- There is little data and liquidity to "price" these companies. SecondMarket and the other markets like that had this issue as well. Everyone is interested in Facebook and Groupon when private. After that, nobody knows or cares. And the interest is based on popularity - not on fundamentals of companies.

- The audience for this type of thing is relatively small - startup enthusiasts, startups themselves and maybe VCs. It's not like Hollywood where virtually anyone has an opinion.