Due to the request of Vitruvius Otoko in the comments, I've looked for a reliable source to all this and found a post by Blizzard Entertainment themselves. Here it is:
In addition to all the other benefits that we believe ultimately come from having everyone online such as an active, centralized community, a popular arena system, accessible character storage, etc. etc. Diablo III is built on a client/server architecture, which means not all the data for the game or mechanics reside on the client (your computer).
This is not too unlike World of Warcraft where the world itself, the art, the sounds, etc. are on your machine, but all of the NPCâ€™s and enemies are controlled by the server. Diablo III doesnâ€™t function in all of the exact same ways, but things like monster randomization, dungeon randomization, item drops, the outcomes of combat, among others, are all handled and verified by the client talking to the server, and vice versa.
Weâ€™ve learned a lot from this type of architecture from World of Warcraft, and the added security and oversight it provides. It allows a great deal of control over the game at all times for all players, so if we know thereâ€™s an issue or bug we can usually address it right then and there through a live hotfix. Hotfixes canâ€™t be used for everything, weâ€™re still going to have client patches, but weâ€™re definitely looking forward to being able to deliver a consistently high quality experience to all players simultaneously through processes like hotfixes.
In addition there are some pretty intense security concerns. While thereâ€™s never a fool proof solution to stopping hack and cheats, weâ€™ve found that a strict client/server architecture is a huge barrier for their development and use.
Ultimately we made the decision to make the game client/server based because of the security and quality it can provide to those playing, and as a bonus it reinforces a lot of our ideals for a thriving online community.
Source: A post by Bashiok, a Blizzard employee, on the Battle.NET forums.
Diablo III requires a permanent internet connection to play. However, what it doesn't tell you is that the requirement is not just forced -- it is actually required.
Diablo III servers don't just keep a constant connection with your computer, they do the number crunching. They calculate damage, AI, loot, actions, the whole thing. You are playing one-user multiplayer, not single-player. Unlike previous Diablo games, your computer does nothing but create the scene. Sure, sometimes it compensates for missing data and lag -- just as any online game does
-- but just like World of Warcraft, you are playing on a server no matter what.
This is more than digital rights management. You are sold an incomplete product
. Blizzard market Diablo III is an RPG with online features
, implying offline is
possible and not the main focus. This is false. Instead, you are buying a MMORPG
in which you are playing alone
. When Blizzard pull the plug on Diablo III servers, you will have a digital or physical paperweight. (You might question that statement considering Diablo II servers are still up. But that is directed at such products in general, which are only usable as long as the developer or publisher feels like it.)
Unlike Ubisoft's Online Services Platform, your games are non-functional if you don't maintain a connection. If your connection is flaky or if the server is far away, you will experience game issues: rubberbanding, lag, errors and maybe even discarded actions -- in situations of extreme network congestion your "click" may not register in time or register at all. This is one example of it.
(And this is another
One example of discarded actions prevalent in online gaming is Minecraft multiplayer. If you own a network card made by Atheros or Realtek, you cannot play Survival Multiplayer. Despite efforts made by Mojang to cut back on traffic, Minecraft sends an immense amount of data back and forth that these brand cards simply can't cope with. The result is lag, changes that aren't seen until later and sometimes even having the server undo your actions because your network card didn't send the actions to the server on time. The server thus determined your actions to be impossible and reverted them.
That's why Diablo III's online-only requirement is a real
requirement and not just DRM, and why it is actually worse
than online-only DRM. I'd have less of a problem with it if Blizzard didn't market the game for what it's not: a single-player RPG with online features, but instead marketed it as a multi-player RPG with a one-user option.