This excerpt taken from the NDAQ 10-K filed Mar 15, 2006.
Regulation NMS is scheduled to become effective in stages throughout 2006, although the SEC recently announced that it may delay its implementation. Regulation NMS will change the method for sharing market data revenues under our plans. The changes will introduce a quote component to the sharing methodology. Until the rule becomes effective, the revenue impact of the change is not completely predictable. Because Nasdaq is an active quoting exchange participant, the impact on our Nasdaq-listed revenue should be negligible. Nasdaq also receives a share of the data revenue that is generated in non-Nasdaq-listed securities because of our quoting and trading success in those securities. Additionally, due to our electronic nature, and thus our active quoting behavior in non-Nasdaq securities, the Regulation NMS-generated change in the sharing methodology may have a positive impact on Nasdaqs share of the non-Nasdaq market data revenue. To the extent that our trading in NYSE securities increases, our share of the data revenue should also increase. A full discussion of the provisions of Regulation NMS in contained in the section entitled BusinessRegulation.