Whoops. Cory Doctorow writes:
If my conjecture about Linn's offense is correct, then she has not violated copyright, nor has she done anything that would upset a publisher. She's merely violated the thousands of words of impossible fine-print that comes with your Kindle, Nook, Kobo, and iPad, as have all of us. This fine print will always have a clause that says you are a mere tenant farmer of your books, and not their owner, and your right to carry around your "purchases" (which are really conditional licenses, despite misleading buttons labelled with words like "Buy this with one click" -- I suppose "Conditionally license this with one click" is deemed too cumbersome for a button) can be revoked without notice or explanation (or, notably, refund) at any time.
And here is the original article and series of emails from the affected user, via Martin Bekkelund: http://www.bekkelund.net/2012/10/22/outlawed-by-amazon-drm/
PS: For the record, I never buy DRM'd files.