Master Plans are tricky. Take a look at Le Corbusier's Master Plan for Paris here. The best design happens when the design is the result of organic limitations. I told a professor I was having a hard time reconciling my love of order with my love of nature. How is it, I said, that I think both the organic spacing of an oak savanna and the ordered symmetry of the Parthenon are beautiful? He explained that I was thinking about order wrong. He explained that there was as much order in the oak savanna as the Parthenon. Hunh?, I said, very intelligently. Well, he said, the trees... all of them grow upward, toward the sun, don't they? And then it clicked for me: Order is not something that is imposed. It is the result of organic limitation, which is a function of time.
No one person (again, see Le Corb above) or governmental agency is going to be able to project needs, craft legislation, impose a set of rules and keep everything working by keeping it under the thumb of the Master Plan. David Dejewski mentions that you will never see a child care center next to an adult video store... I wager that you won't see it because at some point, there was one, and people pushed back, crafting the appropriate covenants or rules and regulations. Do you know how master masons knew how high they could build cathedrals with flying buttresses? They kept building them higher and higher until one fell down. Then they knew they'd gone too far.
Good design is messy. A city, like a government, like a living organism, needs to stay in a continual state of input and output. Artificially cutting off the input means it is now out of touch, selfish, starving. It is sheer arrogance to impose a Master Plan, unless the Plan itself is to continually allow for input, output, growth, and surprise through constant adaption and change. That's natural order.