"What a weird thing to spend your time and effort on without getting paid for it."

Oh I don't know, lots of people, not just mentors, spend time here trying to help others, I guess it's a sort of hobby in a way.  And why not!  And the mentors generally know ebay inside-out and can provide knowledgeable answers.  I agree that the advocacy thing though can sometimes make them stand out as being different from most of the rest of the forum.