[evanb]

This move halted the land rush around the fiber access points in New York. But suppose a firm trades both on the NYSE and CHX in Chicago. If there's a price difference on the same stock in the two exchanges, you can buy low and sell high for a brief period (a few ms): if your machines in the NYSE building and CHX building can communicate that price difference faster than anybody else, nobody knows there's a discrepancy to be taken advantage of.