Unfortunately, I believe Facebook toed over that critical mass that has moved it into a long-term dominator of social networking. It has long since passed the point where it's going to just go away and be replaced by something else, like Myspace and other past social sites were. They may not be around forever, but it seems unlikely they'll be unseated any time soon. We are no longer in an age where a bunch of geeks moving on to something new changes the dynamic of the internet. We are now in a time when the average Joe Sixpack and his grandmother don't look for new things, don't try new things, and don't care about new things. They will stick with Facebook indefinitely, the same way a lot of people still stick with the big three over the air networks for their sole television entertainment.
Even if it doesn't disappear, it's guaranteed to change a lot in the future. As the top poster pointed out, this whole namestring-is-unique-token idea is not sustainable nor elegant.
Surely in the future there will be a better way of differentiating ourselves than "john-doe.com", "johndoe.com", "jdoe.me", etc. And what happens when JohnDoe #1 and John Doe #2 are famous people? Who gets the "verified" badge on social networks? It isn't sustainable, and Facebook and others are bound to change this sooner or later.
