The English language is one of the only languages I know of that does not distinguish between formal and informal you. The languages I am surrounded with here, Tajik and Russian, use formal You for new acquaintances and older persons (it is vwi in Russian and shmo in Tajik) and familiar you for friends (ti in Russian and tu in Tajik). There is one aspect which is very interesting about Tajik's use of use of formal you which is different from in Russian and other cultures.
In Russia (and in Germay) ALL familiars, including adults and parents are addressed with the informal you. But in Tajik culture husbands and wives call each other shmo or vwi and certainly all children address their parents in the formal. I think this is so interesting to look at the cultural implications of having such usage: it is obvious even in speech practices that the family is the most important entity in Tajikistan, though sometimes I, as a Westerner, feel the respect as somewhat of a division, (but that's probably just because even the concept of different "you's" is foreign to my culture). But perhaps the formal you in the family also has to do with the fact that husbands and wives often do not know each other before they are married and there remains this distance between them in marriage, though I can really only look at arranged weddings from a Western eye. All I can say is that the use of shmo and vwi in the family facinating to me, and is probably something I could research further if I did not have such time and language restrictions.