Ever since the change of major North American stock exchanges to a for profit model they have all become infected with High Frequency Trading as the emphasis has changed from quality of trade executions to quantity of trade executions and there is only one winner. An algorithm trading machine.
Need a deeper explanation on the effects of Dark Pools and HFT? Skip on over to BNN and watch this segment with Doug Clark from ITG Canada.
http://watch.bnn.ca/business-day/business-day-am-may-2013/business-day-am-may-24-2013/#clip933397