I have observed a growing trend in which people substitute "no problem" for "you're welcome" as a response to "thank you". In particular, it seems to be an increasingly common response from servers and store clerks.

It seems to me that "no problem" isn't appropriate for *all* situations as a response to "thank you", such as when I express thanks for receiving a cup of coffee at the local doughnut shoppe. To me, responding "no problem" to "thank you" implies there might have been a problem, which was somehow narrowly averted.

Are there specific situations in which "no problem" is appropriate to use as a substitute for "you're welcome"?