DRM is not really an issue with a Kindle (or a Nook) because with Calibre you can automatically strip DRM from files and convert from any format to any format.
It is trivial to buy from non-DRM sources and read those books on a Nook or Kindle.
Amazon once removed copies of books that it sold that it didn't have the right to sell and promptly said they wouldn't ever do it again.
They also once canceled a woman's account (which may have wiped her device) due the kindle being resold or something. I don't really remember. I just remember that people made enough of a stink that they gave her back her account.
What really bothers me about Amazon is that their Kindles phone home with data about the books you read/location data/etc. Well, unless you keep your antenna off or manually kill that process.
And B&N helped kill all of my local bookstores before Amazon was even a thing. As long as authors get paid to keep writing books I don't even care anymore.