Very interesting article by Michael Kozlowski. I never knew this. You don’t BUY an ebook, you license its use. So, if you “buy” from a store that goes out of business, you lose the ebook.
To be clear, when you buy ASS from me, I will happily send you the file. You will own the book. I will also offer it on major retailer’s sites, so you can license it from them.