[ido]

This is very old-fashioned & I guess geographically dependent: we used to live in Vienna where you'd expect to use Sie (formal) with any adult you don't personally know where as we now live in Berlin where everyone uses du (informal).

Either way nobody who isn't an asshole will get a non-native speaker in trouble for mixing these up & even in Austria my experience was that they will just be a bit perplexed but continue speaking as if the "du faux pas" didn't happen.

[StavrosK]

It was a bit surprising to me to see that in Spain you only use the formal plural with much older people, if then, whereas in Greece you'd use it with any stranger that wasn't about your age AND you had some rapport with.

I guess I expected cultures to be similar in who gets the polite treatment, but they're really not.

[collyw]

Latin American Spainsh seems to be a bit more formal and "old fashioned", but varies a lot from country to country.

[type0]

Greece is east European in that regard, possibly influence of orthodox church if I would guess.