A few days back one of the MobileRead forum members contacted Fictionwise and asked when they will start selling ePub formatted books. As they noted in the post, BooksonBoard are currently the only online bookstore that are selling commercial ePub books.
UPDATE: We should not forget that O’Reilly have a small selection of titles that come as an eBook bundle, included in that bundle are books in the ePub format.
Fictionwise replied by stating that “We are currently making our plans for epub compliance over the coming months.”
However, it seems that one of the biggest hurdles for them is how to encrypt their titles, “each vendor is currently using their own proprietary encryption scheme for epub.” DRM isn’t going to go away anytime soon so it’s understandable that they need to work out these issues before they can move forward.
An interesting point they made was that there are still very few publisher supporting ePub at this time, yes more will follow suit, but until they do the number of available titles will be limited.