Circling back again to Robert Sanders' take on current VoIP numbering attempts, I'd like to place my Xmas wish into perspective:
It appears to be widely accepted that users of disparate SIP-compatible VoIP providers will always be able to call one-another via complete SIP addresses that follow this format: sip:username@some_provider.com . When you think about it, this is really frickin' cool. Just like e-mail ... right?
Well, hang on a second, e-mail is done over a computer with a full keyboard, whereas talking to somebody over the Internet should really emulate a phone interface, with numbers and numbers only! Because, after all, that's what people are used to.
When we sign-up with a VoIP provider we typically get a number assigned to us. We right-away confine ourselves to the mindset of using numbers to identify people. Since there is no official globally unique numbering scheme, the number we get allows us to only be able to easily call users who belong to the same provider. Users of other providers can't reach you through that number alone unless the device through which they call you allows them to type your provider's address. In a world where the traditional phone system is clumsily emulated, users need to know a "special code" that "connects" users of provider A with users of provider B. Another code will be put in place to go the other way.
All this clumsiness for the sake of sticking to numbers. Because not only do we want to emulate the traditional phone system in a new lucrative gold rush for globally unique phone numbers, we want to replace it, and we can't seem to make this happen soon enough.
That Xmas wish is the manifestation of a yearning to place a greater onus on smarter, connected devices, with better input mechanisms: keyboard, networking, address book, synchronization, interoperability, and all that jazz. All mobile phones have already been evolving this way: who actually keys-in numbers to call somebody on their mobile phone? Once human interface issues have been addressed, we should never have to limit ourselves to numbers to "call" someone: A full SIP address ought to be a perfectly viable alternative and, in most cases, completely transparent to the user.
1849: "I'll call you". 1965: "i'll e-mail you". 2004: "I'll SIP you".