I'd bet that they have publishers complaining about their stuff being available as an easily-copied file online. Book publishers are quieter than the RIAA, but

I'd bet that they have publishers complaining about their stuff being available as an easily-copied file online. Book publishers are quieter than the RIAA, but they've got very strict ideas about what's good and what's not. I would bet they're the ones who want DRM. Outside of the Kindle store, you can add books of any ebook format, DRM or no DRM. Most of my Kindle is entirely open. Amazon likes open formats, and they're trying their best to support what they can.