That's a really neat idealistic idea. And most of the modern "no borders, no nations" calling people are thinking of how easy it would be to travel.
As it is with all idealistic things, there would be a consideratble amount of people who would abuse the system to engage in unjust or criminal activities (take all criminally-minded people on the world and add some opportunistic ones on top who discover their chance). Just as it is on Steemit with the spammers and cloggers. How would you want to flag the real-life perpetrators?