There is another disturbing trend in the textbook racket (I call it that because it's exactly what it is) that is not mentioned in the article. That's the trend for publishers to release university specific editions. This seems to be mostly involving MIS and business students at OU for now, but will eventually make it's way into all majors I'm sure. This keeps people from being able to sell their books to other students online, even students at their own school.
For example, a girl I work with is an accounting major at OU. A lot of the professors in the Price College of Business have worked out some of kind deal with the publishers where their textbooks are specifically written for use at OU and also come with extras that can only be used by an OU student. That means you can't buy the book online from someone at say Oklahoma State, for example, nor can you sell it to someone at say Univ. of Kansas. Also, they will change the edition the very next academic year, if not the very next semester, and completely rework the university specific material (homework problems for example) where you cannot even use a used copy of the book for the class. What really sucks for people who are MIS majors and engineering majors and the like is that their books can sometimes cost $200-300 per book and once the semester is over, that book is pretty much obselete and you're stuck with it.
It's all pretty disgusting if you ask me and for those of us who are paying for school on our own, we're getting tired of it. Fortunately for myself, being a philosophy/history/classics major, if I get to the library early enough I can check out virtually all of my required texts for the semester and not have to pay a dime...provided the professors don't require me to have a very specific translation!