From Boing Boing

Ultimately, a hardline This-or-That, pigeonholing system of defining genre and works is far more trouble than it’s worth, and can do a great disservice to works that defy easy categorization. Most traditional systems in the publishing industry fit into the pigeonholing system. BISAC Codes (basically trade publishing’s official genre system) are fairly granular, but totally fail to keep up with the proliferation of sub-genres, and the genre categorization systems of all of the major ebook retailers fall victim to the same This-or-That approach.

Oh man, so much this. That said, this approach would be fine for online markets, but how would it work in a physical bookstore? The problem would still be there.