Can I ask another question about contracts? Why do publishers want all the rights to my book, worldwide and in every possible format, even when they say they probably won't use them? For example, my publisher wanted the audio rights even though they said they probably will never put my book on CD. What if I really want it on CD? Do I have any say in this?
One reason publishers ask for rights they probably won't use is for quality control--to prevent you from selling those rights or exploiting them yourself in a way that would be detrimental to the sale of your printed book.
Since you mentioned audio rights, I'll use them as an example. Some publishers automatically create an audio version of books they expect will sell reasonably well. Other publishers wait to see how the book is selling before they commit to an audio version. If sales don't reach a certain level within a certain amount of time, no audio book. But they don't want you to go out and create your own audio book because if you don't know what you're doing and you don't do a professional quality job then that will act as a detriment to the sales of the printed book.
In addition to quality control, publishers want to control the public's access to your book in a way that will boost sales, rather than replace them. They want to make back their investment and make money for you. Having your book out there as an uncontrolled e-book or in rampant serialization is not in your best interest.
Bottom line, unless you're really familiar with the industry and a whiz at contract negotiation, you're not going to be able to sell these other rights yourself anyway. So in most cases, it's in your best interest to go ahead and give these rights to your publisher--who may be able to sell them for you. Most contracts have a clause addressing this, splitting the revenue from the sell of rights 50/50, after expenses.
Now, it's a little different on the national market when you have an agent to represent you. In that case, the agent negotiates for you and separates the various rights, selling them to different entities.