Regularly buy ebooks from Amazon for my Kindle, admittedly mostly at the cheap end of the range, either something I want to re-read for the first time in years or something that looks like it might be worth a look for 99p
Everything I buy gets backed up to a separate HD, just in case.
So yes, I was rather miffed to discover last week that I can't download directly any more and have to send the file to my (completely legit and un-jailbroken) device and then plug it in to a laptop to back it up.
Obviously, once it's there I also break the DRM, if I've bought something it's mine and I don't trust proprietary file formats. If Amazon make it impossible to do that there will be a rethink about where I source my ebooks from....