SimCity's launch has been a disaster, and chiefly due to its always online nature. Gamers have had trouble installing the game; even gamers installing from disc couldn't complete installation without some online files. Those who did install the game waited on long queues just to play - even if they wanted to play solo.
EA had placed atitled, "The Benefits of Live Service", and explained everything, including the simulation engine, was server side.
The situation has been so bad, Electronic Arts is evena refund for the game. One site even reduced their 9.5 review score to 8 due to the online issues.
Stay tuned as this issue is in flux.