Morning, Michael,
In reading about DRM (Digital Rights Management), I see nothing about an ability to remove e-Books from a users e-Reader. What I did find, however, are articles on removing DRM and this link about publishers beginning to remove DRM:
http://kevinomclaughlin.com/2012/04/25/publishers-begin-removing-drm-from-ebooks/ on their own. I cannot see anyone ever removing an e-Book you paid for. Kindle, for example, allows you to install your books on any number of devices as long as you register them (I've done this with three devices).
DRM is encryption used for copy protection. I certainly don't want to get into the age-old argument of copy protection, we can leave that for another day.

I've read several articles about how an e-Book can be removed (all from various interpretations; however, I've never heard of this happening.
Best Regards.