Add to that the almost 5 billion subscribers addressable by SMS, and you see the enormity of the problem standing in the way of reaching a single method of addressing. From a global standpoint, while it would be nice to undo several generations of telephone number usage, we are extremely far from that point.
Instead, what we're likely to see is different communities settling on a common manner to register a person that will span multiple communications mediums or channels. On mobile devices, the common messaging client is now standard, where you can receive or send SMS or MMS, depending on the type of media you include - the client is intelligent enough to decide if a message is an SMS or an MMS message. In their own way, Facebook has extended that intelligence to span their IM or chat community, e-mail and SMS, itself. I expect them to further integrate other communities, e-mails and even phone numbers into that client.
Doing the same on a global scale will be a much larger challenge - and one that will probably be incrementally undertaken. For example, if you want to simply contact me as 'Bill Dudley' or 'William Dudley,' then you have to separate me from all of the other 'Bill Dudleys' and 'William Dudleys' that are out there - meaning today, you have to map my name to one or more of my addressing methods - that is, one of my e-mail, IM, or telephone numbers. However, I may not want to be found, or I may want to remain anonymous, so using my name may not be the optimal way to universally address me. So, in many ways, we are back to square one - I'm left with my five anonymous phone numbers to be given out as I see fit.
The upshot: On a global basis, it will be extremely challenging to move 5+ billion people from telephone number based ecosystem to one that registers some, other addressing scheme to reach people, businesses or enterprises without multiple 'social' or 'enterprise' communities. Of course, the biggest community of all is the global PSTN (Public Switched Telephone Network), based on the ITUs E.164 standard, which defines the international public telecommunications numbering plan or the format of telephone numbers around the world.
We'll probably always have to map telephone numbers, e-mail addresses, IM handles, and other addresses to our friends and enterprises, through various clients or apps. People will need to be smart about it, as everyone will have different preferences as to how they will want to be contacted. It all began with the simple, automated contact list. Now, Facebook has taken this to a new level, by integrating various forms of 'messaging channels' into a intelligent, universal client or as they call it the Social Inbox. I think this is a great start and one that will evolve across a variety of 'communities' and not just Facebook. Time will tell.
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