> Small countries like Denmark tend to have a much more well-behaved population than large countries. I.e. they queue nicer, they are more likely to return something they found, etc. (game-theoretic research suggests that such a culture is a symptom of having a high likelyhood of meeting again - thus offering more opportunities to punish bad behaviour).

The likelyhood of meeting again also depends on population density and the migratory patterns of the society in question. I'm guessing that this research you refer to assumes that the society is fair and each member is treated equally.

Punishing someone on the internet is very hard, especially if they retain their anonymity.