There are so many players in the exchange game these days that it's hard to handicap the field. BATS has made a huge move as of late, and has become the third largest trading venue, behind the NYSE and Nasdaq. It has certainly shaken up the two big boys with its aggressive pricing as of late. BATS has filed for exchange status, which might give it another boost. This week, BATS executed 1.2 billion shares in trades, a new record for the upstart, according to Financial News Online. More than anything, the service indicates that top Wall Street banks, most of whom have invested in the firm, are bent on breaking their dependence on the top exchanges. For buyside traders, the complexity in order execution is an issue still searching for a solution.  

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