~~There's another fine thread here about wheather learning lays at the feet of the student or the teacher. I believe it's a mix of the two, a connection and balance that makes for optimum learning. You may call someone 'Sensei' because of their position in the dojo, time in grade, experience, etc., but if they don't, or aren't able to, really instruct then I don't consider them an 'instructor'.
~~To me sensei is someone who's gone before me and instructor is a teacher, whatever the rank or title. The ideal is when both come together.
~~So there...