While I am envious that upcoming generations will not know the absolute joy of lugging around Chemistry, Physics and Math tombs, I am a little weary that this plan will eliminate the used text book market. I, for one, certainly bought more than one used textbook for less than 50% of the price of a new text. I also had professors recommend going to the off-campus, unaffiliated book store for used texts rather than going to the for-profit on-campus book store in the student union.
The used textbook market was on shaky ground well before ebooks arrived on the scene. Every year, publishers force new editions on the market, making changes to the exercises (so old editions are incompatible with new ones) but making no substantial changes to the actual learning material. Some instructors prefer to assign old editions so their students can find cheaper copies, but most don't care, and others are even contractually obligated (via the school) to use only the newest edition.
If a new e-textbook is under $15, what's the point of seeking a used one? Even if that were an option, you wouldn't save much, and I would expect e-textbooks to be updated more frequently, so you might be missing something if you bought last year's e-textbook.
I suspect with lots of students they sell their old textbooks to save space as much as to recoup some of the cost (or get some money for beer).
