There have been cases where, due to rights issues, Amazon removed books from its inventory, and they disappeared from people's Kindles. Other Kindle users have found books removed or their entire library deleted because they moved to a new country. It's all within the terms and conditions you agree to when you "purchase" a Kindle e-book. You don't own any of it; it's licensed to you, and that license can be revoked. (This is also the case for online movie services, etc. - even though you can "buy" perpetual access to a film, it can be deleted at any time. Presumably, the same with downloaded games and other media.)
I find e-books very useful (and they can be a lot cheaper than their paper versions). But if it's a book I intend to read more than once, paper is the way to go. Paper books are not subject to regional rights agreements (well, they are, which is a whole other discussion, but if you can get hold of a book published overseas, there's nothing stopping you bequeathing it to your descendants). Paper books can't be summarily repossessed by the seller. Besides, they look, feel, smell and read better, except that copy of Magician that got left outside that one time and now it smells funny.