Jaye Manus has a good post on how many conventions about books--even the prevalence of the novel--are the result of the economics of the old traditional-publishing industry. Take away things like the cost of producing a physical book and the limits of shelf space, and the possible formats really open up.
And this is a fascinating article from a few months ago in The New Yorker about K-pop (a.k.a. Korean pop music). While obviously performing songs is different from writing books, I do see similarities (the article exists, after all, because digitization has made it possible for an American writer to become mildly obsessed with a K-pop girls' group). The author writes:
When an entertainment industry is young, the owners tend to have all the power. In the early days of the movie business, Hollywood studios locked up the talent in long-term contracts. In the record business, making millions off artists, many of whom ended up broke, used to be standard business practice.
Of course, traditional publishing is hardly a young industry, but I would argue that owners tend to have the power when an industry is young because they're the ones who have figured out how to work the system and sell stuff. If they can shut out artists, then the same thing happens--if the only way to sell books is to get into a bookstore, and the only way to get into a bookstore is through a traditional publisher, that gives the publisher all the power.
Anyway, the punch line for the article is that, despite all the effort to sell squeaky-clean, highly-polished K-pop internationally, the first big breakout song was Psy's "Gagnam Style." Oops. Yeah, you never do know what's going to be a hit.