Brad, this discussion is not achieving anything. Please stop. If/when zones get to the size that they present operational or management problems, solutions to those issues will be available, They are already available today. [Moore's law will mean cheaper and bigger RAM chips (and CPUs), 100Gb+ disks are becoming the norm and there are plenty of 64-bit architectures and Operating Systems.] Which solution or solutions a TLD registry adopts will be their decision. Having a structured name space won't make much difference: it just moves or defers the pain points.