Your phone number is now no longer important. It's your identity that matters. And Apple, has once again demonstrated forward thinking vision and leadership.
In reality this is precisely what Yahoo started to do under the reign of Brad Garlinghouse (now at AOL) with the YAHOO ID. At Yahoo they envisioned a world where their user identification was what mattered, and if a user moved from carrier to carrier over time they still remained a Yahoo customer. Unfortunately, many meetings between the carriers and Yahoo likely occurred and in those meetings one could gather that the dumb pipers, those providing DSL access which (i.e. AT&T, Verizon and Qwest) more than likely discouraged their upstart partner from taking the concept too far. Kinda like what Yahoo did with VoIP inside Yahoo Messenger (which is still there) and their plans to clobber Skype (under Brad and now Xobni leader Jeff Bonforte.) Those ideals and ideas got derailed by others inside what quickly became AOL II. Over at AOL the same kind of thinking, use your AIM ID tied to your phone services was likely going to happen until the folks at Time Warner Cable more than likely pushed hard corporately because they wanted to sell phone service over their network, and not let AOL's team do it better (and better it would have been based on my tests.)
So with that as history, Apple has come out with FaceTime, and as BGR reports, your Apple ID, or in reality any email address, becomes how people will reach you.
Apple, now with considerable market share, and with it growing everyday, have a way to say...go elsewhere, but your friends stay with you.
Game, Set. ...not quite match yet...but close.