[danenania]

I think that in the long run, true open borders would be a death-knell for the nation-state. The two central purposes for nations, as opposed to local and regional governments, are regulating immigration and responding to (or mounting) military threats. After societies have intermixed to a certain point, you'll see the death of nationalism and sufficient cultural and religious diversity in the electorates of wealthy countries that declaring war on any other country will become very difficult as you'll always have 20% of your populace sharing a religion or cultural kinship or some other line of sympathy.

Add to this the strain of large demographic shifts on representative democracies and you have the recipe for a break up into a decentralized network of regional and local governments that run things according to their particular demographic make-ups. The correlation we have come to expect between geographical proximity and consistent culture and politics would begin to disappear.

[sardonicbryan]

The thing that is really going to collapse our current national system is crypto currency. Once governments can't collect taxes easily, could easily see us going to a Neal Stephenson Diamond Age style post national, lifestyle group based system.

[VLM]

"20% of your populace sharing a religion or cultural kinship"

Germany/Poland/Russia