Diablo 3 went always-online to help solve this problem. Loot discovery, inventory, and fighting outcomes are entirely controlled server-side. While it's possible that they could have forced separate online-only and offline characters, it's reasonable for them to have decided online-only for all characters and not duplicate the logic and engineering. Not to mention DRM.
With Sim City, it's conceivable that they went this way as well.
I'm sorry but you are wrong here. Diablo 2, while it had online realms where you could bring your single player character, most people chose to play on the battle.net realms where all character info was stored online.
The servers where you could bring your single player character were just a show off for people who used character / item editing programs to create insanely stacked gear and characters, and like I said no one really played on those.
The reason Blizzard went online only with Diablo 3 and SC2, was because the Diablo 2's battle.net was reverse engineered, and there was an abundance of servers that could be played on with a fake CD Key all over the world. I remember specifically in Eastern Europe, we had quite a few servers and obviously with the average monthly salary being like less than $200, no one could afford to buy a PC game. Even LAN centers had cracked versions of all of the games and hosted their own servers.
see http://en.wikipedia.org/wiki/Bnetd
Anyway, my point is that you cannot have locally stored game information that can be imported in an online realm and have a direct impact. People will edit that information to create whatever they want. But if a game requires you to be online, it must be an online game period. If a game can be played offline, there is no reason whatsoever for it to have to force you to use online authentication in order to play in a local environment.
I don't think that's the only reason. Diablo II is plagued with bots and duping. While the balance between client-server data on the Battle.net closed realms is much better than it was with Diablo (where you could just edit your character data locally to increase gold/upgrade inventory online), Diablo II still has the problems of 1) loading the entire level map into memory at once, giving bots the opportunity to path their way to POIs with no effort and 2) reconciling local inventory with the server's inventory after lag spikes and server crashes, which is hypothesized to be the main method dupers use.
But, as could be expected, both botting and duping happen on D3 anyway. And, to your point, during the D3 beta period, there were several devs that were able to reverse-engineer the D3 protocol anyway and create a local server. shrug
There are gamers who prefer to play with unlimited resources and complete control of the situation. Many prefer a sandbox where other gamers cannot mess with their experience. Are you telling me Maxis is in the business of getting between the consumer and their game? That's a losing business proposition if it's true.
Ex: ~20,000 player city's are uploaded into a model. They do a simple calculation based on excess energy, pollution, ect. The result's of that are fed back down and then they run the model again adjusting for new city's and client city updates. Now even if 10mhz per city is used your talking about a 200GHz worth of processing which is far more than an i7 but shared and mostly irrelevant in single player as you could just as easily fake the global numbers.
