"Internally I don't think [always-on 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," said Bridenbecker. "You're guaranteeing that there are no hacks, no dupes. All of these things were points of discussion, but the whole copy protection, piracy thing, that's not really entering into why we want to do it."
Bridenbecker goes on to mention that Diablo 2 offline characters couldn't be used online, which got messy for players and the developer, so this time they decided to "just keep everything clean." As for those looking to play alone, they don't have to interact with any other online players if they don't want to -- but they'll still need that internet connection.