[Sirtel]

But how can copying a file be made impossible? I'm not sure it can, hence DRM (to limit your use of any unauthorized copies). Besides, what if I drop my ereader and it dies, and I lose the file that's on it? And if my computer died, I'd lose my entire library, because with your solution I would have no backup at all.

I agree DRM is a poor solution, but currently there's no alternative for library/subscription ebooks, other than restrict them to proprietary apps only (IMO much worse than DRM).

As for purchases, there should not be any DRM on them. But try and tell that to the publishers... or to Amazon.