> More and more college bookstores are run by Barnes and Noble. At my last college I wanted to use the edition I had used last year and the bookstore told me they couldn't order that version because there was a new version out. This has happened to a collegue at my current university.

It's not just the choice of the bookstore, but of the publisher. Most scummy academic publishers now (maybe 'scummy' is redundant) simply stop printing or selling the old editions.