When did "no problem" start replacing "you're welcome" in the English language? Is this phenomenon an American one, or are similar shifts occuring in other languages? In France, do the young people say "Ce n'est pas un problème" instead of "Vous êtes bienvenu" when someone says "Merci," or is there some other new idiom? edibleplastic informs me that the way you say thank you in French is "de rien", which means "it was nothing." Almost the same as "no problem." So there you go.
I hold the door for someone. He says "thanks." I say, "no problem." As if it were a magnamonious gesture to do him the service of opening the door! "No problem" is surely a sign of the decline of politeness in society.