this is extremely true from a network security perspective for new ISP infrastructure as well. It is very "easy" to start forming layer-2 and layer-3 adjacency between things geographically distributed around a city/state sized area without much regard to security. Will create a huge amount of work to come back and fix later. Whereas if you design the architecture from the start with security in mind (how you're going to deal with your management VRFs, monitoring systems, OOB authentication, NOC and neteng access to stuff in private IP space, etc) it will be much easier to scale.