People have talked at length about the necessity of planning and the need for new towns even garden cities. Much of this assumes that such development is at least in inception state-mandated and directed. Without governments to plan we will only get sprawl. I've never wholly agreed with this argument, the idea that private and voluntary action cannot either plan or develop effective places is misplaced.
Here, from a paper by Shruti Rajagopolan and Alex Tabarrok is a different conclusion:
In the next five decades many entirely new cities with populations in the millions will be built in places where today there is little or no population or infrastructure. Most of the urban development will occur in the developing world where government resources are stretched thin and planning is in short supply. Gurgaon illustrates the scope and the limits of private sector provisioning when the state machinery fails to provide essential public goods. The lesson of Gurgaon, Walt Disney World, and Jamshedpur is that a system of proprietary, competitive cities can combine the initiative and drive of private development with the planning and foresight characteristic of the best urban planning. A proprietary city will build infrastructure to attract residents and revenues. A handful of proprietary cities built within a single region will create a competitive system of proprietary cities that build, compete, innovate, and experiment.
In simple terms what matters is that new cities are planned not who does the planning.