Charles Stross makes the argument on his blog that the use of DRM hurts traditional publishers because it locks readers into a platform (namely, Amazon's Kindle platform). It is an interesting read, and he makes points worth considering, though I'm not sure I'm entirely convinced. I suppose his argument hinges to some degree on the extent to which Amazon's products are viewable on other platforms even if there is no DRM. Are there other eReader devices that read .azw files, for example? If not, then the problem appears to be a combination of DRM and proprietary format that reduces the chances a reader will change platforms. You can convert between formats using something like Calibre, but the conversion isn't always perfect and I wonder if many more average eBook readers would go through that process than the process to remove the DRM.
Here is the blog post: Cutting their own throats - Charlie's Diary
Here is the blog post: Cutting their own throats - Charlie's Diary