I know that some summer classes taught by The Others (aka my humanities counterparts) get very, VERY pared down relative to the fall or spring semester versions. I'm not sure of the exact reasons.
Maybe because The Others believe that students can't handle a week's worth of reading a night? (seriously, there can't be that many pages of sparknotes, can there?) Perhaps they don't want to grade a paper every other night?
I wonder if my students expect to cover less material in my class just because it's in the summer?