This excerpt taken from the NDAQ 8-K filed Feb 20, 2008.
A decrease in trading volume will decrease the combined companys trading revenues.
Trading volume is directly affected by economic, political and market conditions, broad trends in business and finance, unforeseen market closures or other disruptions in trading, the level and volatility of interest rates, inflation, changes in price levels of securities and the overall level of investor confidence. Because a significant percentage of our revenues is tied directly to the volume of securities traded on The NASDAQ Stock Market, it is likely that a general decline in trading volumes would lower revenues and may adversely affect the combined companys operating results. In addition, investor confidence and trader interest, and thus trading volume, can be affected by factors outside the combined companys control such as publicity surrounding investigations and prosecutions for corporate governance or accounting irregularities at listed companies.