I recall reading a column about this subject, so I claim no creative rights to the idea, however I was infected by this observation and can not quite shake it, its become that song that will not go away.
Here is the setup, I go to a store I buy something that requires some interaction between me and a sales person, we finish the transaction I say thank you and the person responds “Not a problem”. Now I scratch my head and think “uh yea I bet it was not a problem, isn’t this your job?’. Not quite sure how this phrase seeped its way into the vernacular, but I hate it. What does “not a problem” actually mean? It was easy to help you? Was it not problematic so therefore be on your way?