Ebooks are the easiest of the bunch, but I don't purchase a book simply because it's DRM-free. I find the book I want to read, I look for a DRM-free version of it (I'm fine with watermarks as well), and, if I can't find it, I either strip away the DRM or pirate it.

I specifically didn't mention music because it's easy to get it DRM-free. Pretty much every online music store is DRM-free.