Will the internet become littered with millions of permanent monuments to misguided souls, like the little crosses on side of our highways?
I suspect this will happen to any namespace after long enough. Domain names, Twitter handles, Facebook URLs, whatever. Once enough real estate is taken up with immobile monuments to the dead, the living will have to move on to something else.
I also think this will happen well before 100% utilization. After some point, the number of collisions you hit when trying to get a memorable name becomes too much of a burden and you just go somewhere else, as previously described here: http://rachelbythebay.com/w/2012/11/28/namespace/
2 digits of base > 10?
3 digit numbers?
Hardly a tricky problem to solve...
The decision to lock down a domain name in perpetuity potentially affects everyone on the internet and more to the point, negatively affects the people responsible for maintaining the DNS servers and the content servers, etc.
france.twitter.com/user
artists.twitter.com/user