I de-DRM all of my book purchases because I want them always available to me and usable on all of my ereaders, since the ones like the Sonys can't read certain formats, and I tend to switch from one ereader to another depending on my mood.
With my Android ereaders (the Nooks), the point about unbreakable DRM is really moot, since I can read DRM'd Nook books on it, DRM'd Kindle books on it via the Kindle app, etc.
But I suppose out of sheer contrariness, if a book had unbreakable DRM, I'd buy the paperback version instead. Though I have great faith in the ereading community that the unbreakable DRM would be hacked sooner or later.
