Real cities don't live in bubbles, real cities are connected to each other.
People and resources flow from city to city in regional economies. Neighboring cities directly affect each other, and through markets, their actions affect other cities across the world.
Because cities are connected, they specialize and differentiate. That's possible because they're all playing roles in a larger economy. Cities look different because they make a living doing different things. Clusters of cities working together do things that no city can do in isolation.
From the beginning, we built this SimCity to deal with this stuff realistically. We're not just simulating the internal mechanics of cities, we're simulating how cities relate to each other, to resource markets and to the natural world around them.
These are things that we have to do if we're going to model real cities with integrity.
The larger environment that cities live in, and the global markets that they are participating in are all being simulated on Maxis' servers. We're running the underlying simulations that enable cities to transform their regions, to interact with each other, and to move markets. We're tracking the accomplishments of cities and their effect on each other and the larger world.
This is true whether you're playing by yourself, or if you've invited a bunch of friends to come and play with you. Your impact on the larger world matters, and the larger world in turn influences your city. This will be visible in lots of different ways, from changing commodity prices, to leaderboards to global and regional opportunities.
Here's what this means in practice - Your cities won't all look the same, they'll take on specific roles, and it's just awesome to create a region with your friends. It's magical to see Sims come from their city to yours. It's fun to make stuff and send it to a friend when they need it.
When you see the connection between your city and the larger world, your city is more real than it's ever been before.
That's why it's an online game. We'll be showing you more of this at this year’s E3 Expo in June.”
-- Ocean Quigley, SimCity Creative Director
Ocean Quigley on why Single Player in SC2013 requires an internet connection