Ebook sellers have two problems—finding customers, and once you find them, helping them find books. Browsing is one area where the Kindle store needs work, frankly, at least when used from the Kindle. It's fine if you know the book you want, less so if you want to graze through a genre. I noticed a similar problem when checking out Smashwords a newish entry in the self-publishing industry. Smashwords publishes only ebooks; one thing that's nice is the books are DRM-free. They also offer free samples of most of them (very Kindle-like). But when I first looked at the site, it seemed to me that they had put more effort into making it easy to publish than in getting readers to buy the books. I wanted more ways to browse. You could list books by category but there weren't that many categories. And if you use "search" to look for a genre, such as science fiction, you could then list your results by "most recent, "highest rated," and "best sellers." There was no "by author," or "by title" button, and there was no hit list to tell you how many books were on the search results list. But of course, the biggest limitation self-publishing sites have is that while many people go there to publish books, but not a lot of people think to go there to buy books.
That's where Amazon has made it difficult for other ebook publishers to compete; if you don't use CreateSpace, you can't list your self-published ebook on Amazon. You could say that Amazon isn't playing fair, but I'm sure Jeff Bezos' answer would be that selling books isn't a game.