Quote from WinstonTJ:
There was a time when there were huge differences in latency - where even fairly big companies were still using 10/100 networks and gig switches and circuits were extremely expensive.
Today with advances in virtualization technology 10-gig Ethernet is becoming the standard and 10Gig NICs are pretty cheap - for $500 you can get a dual-port Intel 10G NIC (ebay).
Because 1000mbps is now the standard and shops like Verizon have pumped FiOS everywhere we have a pretty decent infrastructure backbone and this has eliminated much of the latency arb that used to exist. That said, there is still a massive difference between colo and non-colo. What was a second is now a millisecond.