What If the Earth Were Flat?

Ilkka Kokkarinen has a speculation on the effects of the world being flat:

I wonder what life and things would be like if Earth was flat and infinite in all directions, so that no matter how far you went, there would always be new geography and people and cultures living there. To sidestep the question where all these people came from, let's say that there is always a finite number of people, but there are so many (and that they expand so fast) that from where you start, you would never reach the edge even if you travelled in the speed of light. What would international politics look like in this world, since for example any possible "U.N." or alliance between nations could ever include only an effective zero percent of all nations? Would there be massive migration of individual people constantly going on, with the hope that logically there must be something much better out there somewhere? What would life be like for talented people in various fields, since they knew that there are countless people out there who are even more talented in that field, and somewhere out there everything they can do is obsolete?

Effectively-infinite populations should erase the obscurity trap, in which nobody uses a potentially-important technology because you can't find experts in it and nobody tries to learn it because you can't get a job in it. In a very large society, hobbyists can jump start nearly anything.

Increases in population size can affect moral standards. At present, in a world of a few billion humans, there are plausible-sounding calls for the currently most-powerful nation to right every wrong (e.g., “We can stop the Darfur famine.”) and plausible-sounding claims that picking and choosing between wrongs to right is hypocritical. I suspect that on an infinite plain, similar ideas would be regarded as obvious nonsense.