Thing-ology has an interesting post on the economics of ebooks in libraries. They argue, essentially, that libraries need site-licensed copies of ebooks rather than ones tied to specific physical devices; this will split the library and direct-to-consumer ebook markets and allow for runaway rental/licensing costs for library ebooks. There’s an apt comparison to runaway journal costs for academic libraries.
I think this argument has a lot of merit to it (although I do think the markets aren’t entirely split, and the existence of the consumer market puts a cap on the licensed market; your site license for 25 simultaneous uses can’t cost much more than 25 direct-to-consumer, device-linked copies before buyers start fleeing). It also reminds me of the horrible angst that is the textbook market — it points out that for many books prices are held down because used books compete with new, and this downward pressure stops holding in a rental-based model, because there is no secondary market. There is, of course, a thriving market in used textbooks, but one which publishers vigorously combat via incompatible new editions, included software, and (soon and increasingly, I’m sure) digital textbooks on a rental model — just like the ebooks picture Thing-ology paints for the library.