Bob and Dawn, I have invested every bit as much time, sweat, and dedication to my books as you or any other author out there. In this issue, I doubt for a moment that the OP would actually believe they own the rights to an eBook upon purchase, any more than a person who buys a physical book believes they own the rights to it beyond possession of the paper and ink.
To quote you, Dawn: "You may not copy, transfer, etc. without express permission from the author." Yet, take into consideration KDP guidelines such as: 5.2.2 Kindle Book Lending Program. "The Kindle Book Lending program enables customers who purchase a Digital Book to lend it subject to limitations we establish from time to time. All Digital Books made available through the Program are automatically included in the Kindle Book Lending program." Thus, when you publish through KDP, you are giving your express permission, albeit within reason.
Smashwords' FAQs support your (and my) contentions: Smashwords books are licensed for your personal reading enjoyment only, so you are not legally allowed to copy, share, or email the book to others, and you are not allowed to resell or distribute the book to others. Smashwords authors are trusting you to honor their copyright and hard work, so please do not breach their trust in you.
But, if you "un-publish" a book on Smashwords, anyone who purchased it prior to your "un-publishing" still has access to their purchased copy of the book. Again, this reinforces that the buyer purchased a copy of the book that they "own", but they do not own rights to the book.