The post has some interesting points about genre, but the point I want to make is that genre in print books can be a limiting factor. Bookstore clerks need to know where to put a book. But in a virtual world, books can be tagged with as many labels as apply, which could lead to mystery readers tripping over Harry Dresden. The "get a free sample" feature that works so well with ebooks could make them take a chance on something new and like what they read.
Score one for ebooks!