From Diablo Wiki
Players can play alone, or in multiplayer games with up to three friends in the PvM aspects of Diablo III. The PvP Arena allows up to six players at once in 3v3 teams, and there may be other, online-only aspects of the game that allow larger numbers of players to join the same game type. (Guild halls, trading areas/games,
There will also be offline single player in Diablo III, but those characters will be unable to play over Battle.net, and since there is no LAN support for Diablo III, they'll never be able to play in a multiplayer game. They will also be unable to access numerous Battle.net-only game features, including trading, the Arena, the shared stash, and more.
The planned level of non-support for single player in Diablo III is a very controversial issue and one that many fans have spoken out against.
Offline Single Player
The developers have stated their desire to "discourage" players from using the offline play mode in Diablo III. Blizzard's stated reason is that playing online (solo or in a group) is more fun, that players will want to earn Achievements through Battle.net, that you can then use your characters in the Arena, that you'll have access to friends lists and other (Facebook)online social networking tools, that that having separate, non-B.net, single player characters in Diablo II was confusing and no fun.
Their unstated desire is to fight piracy. An understandable desire for a company that wants to make money, and one which was clearly the driving force behind removing LAN support from Starcraft II and Diablo III. Players can play over a LAN with a pirated copy of the game, but can not do so via Battle.net.
Blizzard has not yet revealed details about how they'll be "discouraging" offline single player. Clearly PvP in the Arena, as well as Achievements will not be included in offline single player, but it's not known what other features will be missing.
Fans have objected to this plan for numerous reasons. While its possible to simply play offline SP chars all the time, most people want to play online some of the time, and offline at other times. And plenty of people are limited to only playing offline.
The most common is the most basic; people just don't like having their options removed from products they are paying for. About the least popular Stacraft 2 "feature" was its lack of LAN support, and while Diablo players haven't been quite as annoyed about the lack of LAN support in Diablo III, no one is very happy about it. Players recognize the necessity for Blizzard to fight piracy, and that making the online play experience more robust is a good way to do that. But them removing features to force online play feels very manipulative and corporate/Bobby Kotick/evil.
The related issue is poor or expensive online access, or Battle.net downtimes. Common fan objections:
- No internet access at home.
- A metered internet connection that gets very expensive over a set limit.
- Slow dial-up access.
- Live in a region (especially South Africa, Australia, and New Zealand) with no local Battle.net servers and unplayably-high latency to servers in Europe, Asia, or America.
- Realm down or other Battle.net problems = you can't play your online characters.
Online Play Encouragement
The other side of the coin from "discouraging" offline SP play is encouraging online SP (or MP) play. The developers have been vague about these benefits thus far, and aside from mentioning that there will be numerous Battle.net Achievements for Diablo III, the Arena game mode, and a stash that is shared between all characters on the same account, little has been revealed.
The developers have let us know that there will be numerous end game options other than PvP or boss/level runs. We may see features like larger raid style games, special bonus dungeons, and other features that can only be accessed through Battle.net.
Blue Comments on Single Player
Bashiok commented on their desire to discourage offline single player in October 2010, kicking off one of the most contentious fan debates about anything yet in Diablo III.
A lot of us, myself included, and probably a lot of you and your friends had the exact same Diablo II experience. You get the game, start playing, your friend says let’s try co-op, and when you log in your characters aren’t there. After a slight freakout moment and potentially some use of Webcrawler to search the World Wide Web with Netscape 6, you realized or figured out that you had to start over. That’s actually an experience that can cause someone to stop playing the game. Maybe you or I let out a huge sigh, and maybe a brief mourning period after realizing the last 60 hours were completely wasted, but we pressed on. That’s not the case for everyone. Maybe most people. I actually refused to start over for a while and continued on in single-player before finally jumping on Battle.net. Who knows what a lesser man would have done…So, if we can get people online and creating character on Battle.net from the get-go, there’s less chance of that catastrophe. But there’s still a play offline option, if you should need it.
Bashiok's argument that many people weren't bright enough to figure out the difference between single player and multiplayer characters didn't win many converts in the very contentious fan debate about this issue.