It's really too bad self-publishing has such a bad rap in the industry. Generally people assume a book is self-published because it wasn't good enough to get picked up by a traditional publisher, but really there's a lot more to it than that. Many of the books that do get picked up are crap, just marketable crap. And there are plenty of reasons why good authors choose to self-publish — for the better royalties, for example, or to avoid giving up rights to, and control over, their work.
With all this in mind, I really get a kick out of hearing self-publishing success stories — such as this one, from NPR, about a self-published Christian novel that has made a number of bestseller lists.
Of course, it definitely helps that Christian fiction is a hot genre right now, not to mention that there's lots of community networking opportunities there (which can help sell books). Although in William P. Young's case, the marketability of the book was inadvertent, it just goes to show that self-publishing success requires as much business sense as writing skill!