It's a complicated issue, not only because of the prevailing attitudes about publishing but for technical reasons too. How would an e-book be formatted to prevent people from just passing around a single copy a mission times, for example?
In publishing, there's also a significant stigma attached to self-publishing as opposed to going through a publisher - it tends to be taken as a sign of failure, that a book didn't deserve to be published. It's not an attitude that's completely without foundation, since a lot of junk does get self-published, but on the other hand an equal amount of junk gets accepted by publishers. Despite all of the prejudices against self-publishing, modern publishing certainly needs alternatives to the mainstream channels of publication as the industry grows increasingly centralised and closed to new authors, to back-list books, to unusual ideas, and closed to the authors with moderate sales who aren't going to become media phenomena.
Perhaps a good compromise between the multinational publishing houses and self-publishing can be found in the small presses, like Babbage, which is keeping some of the old Blaylock books in print.
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It may be more difficult for them to promote a previously unpublished book, though, since they would need to do some promotion to make people aware of it.