Originally Posted by Neil Yamamoto
For me, it's pretty simple. I don't accept anyone as a student unless I see traits in them that I would seek in someone as a friend. Now, whether we become close friends or not doesn't really matter. In some cases you do, in some you don't.
What matters is the student accepts you as a mentor in what you are teaching, and you do what you can to live up to that. As a student, you try to understand what your sensei is trying to communicate to you and try live up to expecations. Essentially, "Don't be a jerk." goes both ways.
What can easily happen is the line gets too blurred for some people. I'm treated slightly differently on the mat by the guys in the TNBBC than off that mat when we are at the pub. I tend to think it's a matter of the instructor determining the line, and the instrucor's behavior, skills, and personality encourages or discourages how the student behaves. Frankly, it's no different than leadership skills in any group.
I view the subject as extended family by choice, with some hard filtering of who gets to be in that family. I have blood relatives I can't stand, and don't associate with, other blood relatives I respect and spend time with. In the dojo and student setting, I try to make sure the % of those I do want to spend time with is as close to 100% as possible. Can't always be right though, so you just do the best you can to get those who share similar goals and mindset as to what the purpose of training is for with the group.