I can tell a nice UChicago story about Andrew Abbott. My son and future daughter-in-law both took a seminar with him in fall quarter their fourth year. There were about 10 people in the seminar. It went really well, everyone loved it . . . and Abbott (who is a pretty famous, senior professor) offered to continue meeting weekly with the group for another quarter, giving them assignments and leading discussions through the winter quarter. It wasn’t a course, they weren’t writing papers or getting grades, but I think only one student “dropped out” of the completely voluntary seminar continuation. Abbott got nothing out of it other than the chance to teach some students with whom he already had a relationship a little more. I thought that was very cool, and something it’s hard to imagine happening at other elite universities.