Rock, Paper, Shotgun discusses the always-on DRM in the Diablo III beta in an article titled "How Diablo III’s DRM Will Affect You," posted under the heading "Why Blizzard Must Reconsider." This recaps Blizzard's reasoning for requiring a constant internet connection to play the upcoming action/RPG sequel, and in spite of there being a better reason for risking players losing their progress due to crashing than was the case in Settlers VII, says: "it doesn’t make the problem go away, and I want to strongly argue that Blizzard reconsider their decision, in the face of its simply breaking their game. Because no matter how perfect your connection, it will affect you." The author describes losing progress due to server glitches, and grants that this is still a beta, but notes that such glitches are still to be expected occasionally once the game launches for real. He also goes on to outline the following "more striking and regular problem" he has encountered:

You can’t pause. In fact, in most ways, the game acts like an MMO. For instance, quit it, and you’re given the optional cooldown to have your player clear the server properly. But it’s not an MMO. It’s not even close to an MMO. So when I’m playing the single-player game, and I’m in the middle of a frenzied mob, and there’s a knock at the front door, there’s nothing I can do. As happened to me yesterday. Twice. On another occasion I was surprised by a phone call that led to my having to do some other things. I’d safely left my character in a cleared area, but long between checkpoints. When I came back to the PC, I’d been idle for too long and the game had logged me out.

I’d been logged out of a single-player game because I was away for an hour. And thus lost all my progress (although not my items and stats) since the last checkpoint, a long, long way back.

In fact, currently, losing your connection (either by idling or the server going down) resets huge chunks of what you’ve already played, such that the map is blank, and you need to battle through it again. Whether that’s an issue with the beta, or something that will also carry through to the finished game, we obviously don’t know. But it’s another clear example of how having your single-player, offline game require a constant connection is massively idiotic and counter-productive.

Games with occasional checkpoints are obviously a massive pain for anyone who might or need to stop playing at that moment – something that’s not exactly an uncommon occurrence. But a game where that’s the case, AND you can’t even leave it running in the background, is beyond acceptable.