When Amazon bought the market-dominant audiobook company Audible, they promised to get rid of Audible's DRM if there was enough public outcry. It's already the case that many audio publishers (including Random House Audio, part of Bertelsmann, the largest publisher in the world) want to have their material sold without DRM, but Audible and Amazon have gone on to demand that publishers license their material on a DRM-only basis.
Richard is taking Amazon at its word: he's set up "Call an Audible," a one-click site for sending your feedback to Amazon on its DRM policy. I'll be sending them an email: Audible is the exclusive supplier of audiobooks to iTunes (itself the largest distribution channel for audiobooks in the world) and Amazon won't sell audiobooks through its MP3 store, either.
My latest novel is a Random House audiobook and Amazon refused to carry it because it had no DRM on it -- I never thought I'd see the day when Amazon would refuse to sell my books because they didn't have enough restrictions. After all, this is the company whose official (and fantastic) position on used books is "When someone buys a book, they are also buying the right to resell that book, to loan it out, or to even give it away if they want. Everyone understands this." It goes without saying that one of the rights you lose when you buy an Audible book is the right to resell it, loan it or give it away.
I used to be a very dedicated Audible customer: I spent thousands amassing a giant collection of audiobooks. When I switched from the Mac to Linux, I had to rip all those books by playing them out through AudioHijack on three separate CPUs, which took an entire month. The more you spend at Audible, the harder it is to get out.