[bko]

Bare in mind that the system used to be centralized and, as mentioned in the article, was much costlier [0]. The fragmentation has downsides and no one likes redundancies, but it is a direct response to the older, less competitive system. The fact that a decentralized system is better is exhibited in the lower price and the participation in the smaller exchanges.

[0] http://www.bloombergview.com/articles/2014-03-31/michael-lew...

[elecengin]

Completely agree - in the single exchange markets you see a lot of monopolistic behavior with the operators.

In this current, though, we have three major operators with 2-3 exchanges each - many with single digit percentages of market share. I suspect that the savings in execution cost due to competition are vastly overwhelmed by the increased cost of infrastructure for most market participants (excluding the largest firms).