This is an issue that is going to be here to stay. First Amazon and now Apple are moving towards establishing the ability to re-sell ebooks.
Here is a very interesting article about the topic by David Pogue. This link will take you to the article that Mr. Pogue refers to.
As a self-published author I am not a real fan of ebooks being resold. Paperbacks are established in the resale market. I also make a lot more money on the sale of a paperback copy compared to what I earn on an ebook.
Of course, Amazon and Apple don't care about my tiny self-publishing empire and there is no reason for them to do so.
Logic says having one of my ebooks resold is like a free copy I give away. If the buyer of the used copy likes it, he/she may purchase some of my other books. I just don't feel so sure about this idea.
Perhaps it is just I am growing weary of the constant upheaval due to the blinding pace of the digital world and how quickly the technology changes.
At any rate, this is probably going to happen. Self-publishers will need to be ready when it does as it will impact each of us differently, but it will impact us in some way.