If you have an Amazon Kindle, then you should note that you do not really ‘own’ the books you bought from Amazon. The ‘ownership’ concept on the Kindle is different from the commonly understood concept and as it applies to physical goods/books sold/purchased.
This difference arises because of the terms used by the sellers. Sellers use the term ‘licensing’ when selling eBooks, allowing them to take back the goods sold, without any monetary returns.
As illustrated by the most recent example ,  and earlier incidents , , , Amazon is at the liberty to wipe any book from the Kindle at its discretion. If they believe you are ‘violating’ their terms and conditions, you can bid goodbye to all the books you bought. And Amazon will NOT compensate you for your purchases.
Please be aware of this limitation when investing into the Amazon and Kindle ecosystem. The ecosystem is great but comes with some drawbacks, which you should be aware of.
To present the same situation happening with you, Ars Technica is suggesting in  that you should buy books from Amazon and then remove the DRM. Once DRM is removed, the books remain on you Kindle and cannot be deleted by Amazon.
Go legal, but retain your books.
 Amazon closes woman’s account and wipes her Kindle, refuses to say why – http://www.bekkelund.net/2012/10/22/outlawed-by-amazon-drm/
 Amazon Wipes Customer’s Account, Locks All Ebooks, Says ‘Find A New Retailer’ When She Asks Why – http://www.techdirt.com/articles/20121022/07340420786/amazon-wipes-customers-account-locks-all-ebooks-says-find-new-retailer-when-she-asks-why.shtml
 Amazon Erases Orwell Books From Kindle – http://www.nytimes.com/2009/07/18/technology/companies/18amazon.html
 Big Brother: Amazon Remotely Deletes 1984 From Kindles – http://mashable.com/2009/07/17/amazon-kindle-1984/
 Media goes crazy over Amazon deleting ‘1984’ from Kindle, but 99-cent ebook was illegal copy – http://betanews.com/2009/07/17/media-goes-crazy-over-amazon-deleting-1984-from-kindle-but-99-cent-ebook-was-illegal-copy/
 DRM be damned: how to protect your Amazon e-books from being deleted – http://arstechnica.com/gadgets/2012/10/drm-be-damned-how-to-protect-your-amazon-e-books-from-being-deleted/