Back in the mid-80s, when some people at Bell Labs were trying to get the rest of us there onto the DNS bandwagon, there were some people who didn't like it. Pike and Weinberger put out deep theoretical papers like The Hideous Name on relative vs. absolute names and the effects of syntax (available at http://cm.bell-labs.com/cm/cs/doc/85/1-05.ps.gz ), and the Plan 9 naming structure, and Honeyman and Bellovin wrote pathalias to optimize communication paths across bang-space and other namespaces. I mainly grumbled about the unlikelihood of everybody being willing to let some central authority decide whose machines could be named gandalf and mozart given the current anarchic structure of uucp naming, a prediction which proved resoundingly wrong over the next few years as DNS took off like wildfire because it was obviously much more convenient. :-) The main feature of a global hierarchical namespace root is that "There Can Be Only One" (Highlander, 1986). That doesn't mean that other people can't use the same syntax and software to describe a different namespace that may overlap the Internet's namespace and may resolve to the same addresses in many cases, and over the years there have been occasional alternate-root namespaces grabbing a fraction of a percent of the market, and sometimes they've even been administered well enough that their few users don't all give up immediately. But when they do something wrong with their "root", that doesn't mean that there's anything wrong with "the" root - it just means that their users may get unpredictable results, which is something they're mostly used to anyway. The DNS namespace is designed that lots of things can be grafted under it, and much of the DNS name resolution software is designed to resolve local as well as global names. So company example.com with globally-named servers like engineering.example.com or london.example.com can have users who refer to those servers as "example" or "london" as long as they administer their DNS correctly. And Joe-Bob's Alternate Root Services can have locally-usable names like www.example.fun which are also globally accessible as www.example.fun.joe-bob-alt-root-example.net by people who don't use their name resolvers (again, if they configure everything correctly) - but many of the alternate roots over the years haven't wanted to do that, because it makes it obvious that they're not the "real" root, just a wannabe. There have been other global namespaces - ICQ was very popular for a while, and it didn't get bothered by the WIPO-and-ICANN crowd because nobody worried too much about trademark violations in a flat numerical namespace that didn't correlate with anything else. On the other hand, the ENUM proposals do have serious issues of namespace policy and centralization-vs-decentralization - should their hierarchical number space be forced to buy E.164 numbers from the Telco Gods? Should anyone who has a PBX be able to manage ENUMs for extensions under it, and should anybody with a phone number be able to define ENUM numbers under it (e.g. 5.4.3.2.1.0.0.0.1.5.5.5.3.2.1.1 to get extension 12345 at +1-123-555-1000, or fax.0.0.0.1.5.5.5.3.2.1.1 to get the fax machine?)