Zero Hedge will attempt to categorize all the relevant players in FlashTradingGate. This is the initial focus of Senator Charles Schumer's recent campaign for market equality and transparency. As we will undoubtedly miss critical connections between these and other pertinent industry players, we solicit readers' insight as we develop this org chart: we invite readers to send emails to: flashtrading@zerohedge.com with any input.

For a sense of services provided by Direct Edge, Here is the Direct Edge fee schedule.

And here is the July 2007 commentary by Goldman Sachs and Citadel when the two firms purchased a 19.9% stake each in Direct Edge.

"Direct Edge has quickly become a major market center for U.S. equities by virtue of its innovative market model and competitive pricing schedule" said Greg Tusar, Managing Director, Goldman Sachs. "Goldman Sachs is a fantastic addition to the Direct Edge partnership," said Mathew Andresen, Co-Head of Citadel Derivatives Group. "Volumes have grown significantly in recent weeks and we expect that trend to continue as Direct Edge becomes a more important liquidity destination for the marketplace."

For some other, more recent and relevant perspectives by Goldman's Greg Tusar, who has been abnormally vocal about another aspect of HFT, pre-trade monitoring, read here.