Imagine the year is 2045. You are in charge of building a new city center in China. The people are getting a bit tired of mass modern tower blocks and the local government has hired you to provide a space that will be different, someplace the hard working new middle class of southern China could enjoy going to.
You decide that Brussels is a lovely city. So you access to a state of the art 3-D printer.
So how do you build Brussels again? You go to a market place like Second Life and you find a detailed SIM that has executed a design. You have the advantage of being able to walk through it. You buy the designs and then place it on a topographical copy of your area, making what additions you need or changes.
Then you just print Brussels.
I am pretty sure this is the future of architecture. Not sure I like the idea of the real world looking more and more like Second Life, with pieces of great buildings simply placed around without context, but it certainly is the most effective way to start building cities.