David Byrne (of Talking Heads fame) wrote an excellent Wired article summarizing the current state of the music industry. He compares and contrasts six different distribution models and highlights the level of artist control in each. For anyone who thinks iTunes is the artists salvation, be sure to check out the illustrations Byrne provides; they indicate that the inefficient CD distribution model is generally more lucrative for the artists, even with a higher artist royalty rate for iTunes sales.
As you read this article, think about the book publishing world, print vs. e-content, online vs. brick-and-mortar distribution, etc. There are a number of differences, for sure, but there are quite a few parallels as well.