Remember how I said I thought the the D3 always online stuff was mostly arrogance?
Im actually kind of surprised in terms of there even being a question in todays age around online play and the requirement around that. He went on to explain that anti-piracy concerns did not factor into the decision: Internally I dont think [DRM] ever actually came up when we talked about how we want connections to operate. Things that came up were always around the feature-set, the sanctity of the actual game systems like your characters. Youre guaranteeing that there are no hacks, no dupes. All of these things were points of discussion, but the whole copy protection, piracy thing, thats not really entering into why we want to do it.
http://www.rockpapershotgun.com/2011/08/05/blizzard-vp-surprised-by-diablo-iii-reaction/
Pretty much what I thought. To them, it's about the "sanctity of the game." ie you'll play it our way or not at all.