yenz:
I have noticed that when an English or American film has been added subtitles in Danish, the translator has this problem: In Danish we have two ways to address others, the polite "De" and the "du" (thee or thou). When people start using first name, "you" will be translated as "du" but until then, it is hard to find the right word. Within the last 50 years most people says du to everybody, young people do not know the difference, but a story set in the 50s (or earlier) will have to show this differentiation.
The same goes for most European languages (tu/vous in French, du/Sie in German, etc), English being one of the few exceptions. We used to have 'thou', but that's pretty well vanished except in Biblical quotes and some local dialects.
I agree, it does make subtitling very awkward - finding a viable translation for the common French expression 'On se tutoie?' is almost impossible. We also lose some subtleties - the moment when two people in a film switch from the formal to the informal can tell us a lot about what's going on between them.