In finance, a dark pool (also black pool) is a private forum for trading securities that is not openly available to the public. Liquidity on these markets is called dark pool liquidity. The bulk of dark pool trades represent large trades by financial institutions that are offered away from public exchanges like the New York Stock Exchange and the NASDAQ, so that such trades remain confidential and outside the purview of the general investing public. The fragmentation of financial trading venues and electronic trading has allowed dark pools to be created, and they are normally accessed through crossing networks or directly among market participants via private contractual arrangements. - http://en.wikipedia.org/wiki/Dark_liquidity
Go to the wikipedia link and keep reading to understand the full extent of what im talking about.
This should mean with the right legal process in place we can trade bitGOOG (Google Shares)
Just because it says "...for insitutional investors" does not mean it has to be and it is completely done like that. The main features of a dark pool, are secret and anonymously.