Josh Lim, 11/07/2012 04:12:
To corroborate what Beria said: I needed to carry my passport with me while traveling around Europe (except within Poland, where I carried my [national] student ID). And since I was advised not to get a residence permit (stay of less than one year, that's why), it was sometimes hasslesome to convince people that I was staying in Poland. This most notably happened, for Nemo's sake, in Italy, where I was detained at Fiumicino for around 10-15 minutes while immigration personnel tried to "clarify" my status.
Well of corse, this discrimination of non-Europeans can't be eliminated now. :-p And since this is the new track of the thread, I can add that even for us things can get problematic if you forget the ID in the room before leaving for the airport as I did in Poland. :D
Nemo