Well, I entrered Argentina with a back tickett in 6 months, and asked for the 90days automatic tourist visa at the border (and got it), got a bit lost and re-entered the international zone with my stamped in passport, the border guy recognize me, and guide me back in the national zone, up to my luggage. I then crossed twice the border with Chile during the week-ends to get new 90 days tourist visa (and it was clearly way more difficult for an Argentine than a European, also they have special treaty and are neighbor).
Here in Europe, we have mostly no border between 15 states, when you cross one by car, you have a few signs on the side of the road: flag of the country you are entering, european flag, and local speed limits. That's pretty much it.