Secondhand books online - damaging the publishing industry?

Via Confessions of an Idiosyncratic Mind, this report from the NY Times (registration required, I'm afraid), about the effect of online used book sales (especially through Amazon and e-bay) on new book sales. You hear these sort of complaints about secondhand books from the book industry from time to time, and as a regular buyer of secondhand books in shops and online, my response is not sympathetic. All secondhand books have been new books, and why shouldn't the owners of said books get rid of them when they don't want them any more, so other readers can appreciate them? When I was a student I couldn't afford to buy new books very often at all: secondhand books and their sellers were a lifeline. And, OK, I still don't buy that much new fiction, it has to be said (and hardbacks hardly ever); there have only ever been a handful of authors I'd rush out to buy as soon as their latest offering appears in the shops.

It's possible that Amazon in particular - since you can see the availability of secondhand copies right next to the new ones - is making inroads into new book business. But surely this can only go so far, since there will always tend to be a limited number of secondhand copies available (unless a book is so bad or dull that the buyers of the new copies can't wait to get rid of it, I suppose... in which case the secondhand market is hardly the problem). And I don't know about anyone else, but my secondhand book buying falls into certain patterns that are not exactly the same as my new book habits. When I buy a secondhand book, it is often NOT simply the case that I'd have bought a new copy if the used one hadn't been available. Sometimes it's because a book is out of print. Sometimes, well, it's there on the shelf, I sort of like it, I don't know if I'll ever read it, but at that price it won't matter, will it... Sometimes I just want a cheap trashy book to read on the train. Sometimes I get a duplicate just because I like the cover on an older edition (it's true!). And sometimes it's because I'm trying a new author - and if I like it enough, I may well buy new in future (and similarly with library books, incidentally). But it never seems to occur to the book industry that secondhand book buying could act as a stimulant to new sales.

Have there ever been any studies of secondhand book buying? I'd love to know.