This forum usually has posts about the ethics of writing and publishging, this one is about the ethics of book buying. Rather than launch with my own opinions, I'll pose it as a question.
I read this recently on NHI Reviews Online in reply to one of the authors they reviewed that wanted to know why they didn't include an Amazon link to his/her book:
We always encourage people to deal directly with publishers, especially small press publishers who often cannot afford the discounts demanded by bookstores, some of which (not all) take a long time to pay their supplier. Books carrying an ISBN can normally be ordered through various online and other bookstores, but you will usually find that the cost of delivery is considerable. We always, where available, provide links to the publisher and/or author's website. If you wish your readers to purchase from a specific supplier, then your own website should be the place to put that information."
There was a thread recently about supporting local bookstores in the face of high street shop oppression
-- does the same really apply to online or mail order book buying?
-- would you as an author or potential author mind if you got less per book via Amazon or some such alternative, so long as the book was sold?
-- or is it a worthwhile ethical exercise to support the small presses and the author no matter what the sacarifice of convenience?
-- or, ??? anything else??
<Added>Here's the original link for NHI Reviews:
http://www.nhi.clara.net/revfaq.htm