The Markets in Financial Instruments Directive (Mifid) was introduced to harmonise regulation across Europe and increase competition in investment services. Now two and a half years down the road the legislation is being looked at again. Dominique Cerutti, deputy chief executive of NYSE Euronext, is keen this tackles two main side effects of Mifid. One is increased opacity, which he argues can be dangerous for the market. The second Mr Cerutti asserts led to the flash crash of May 6, over-fragmentation, where rules are not common across different venues.