I think the hierarchy might look something like this, in descending
order of desirability:
1. Good planning
2. No planning
3. Bad planning
As I said somewhere back there, a lot of the really awful suburban land
use patterns (uniform low density, high degree of functional separation,
etc.) are more often than not the result of planning code. As the _Home
>From Nowhere_ book points out, the prototypical Main Street America has
been outlawed in many places by zoning rules that keep types of housing
apart, keep housing far from commercial districts (which are themselves
kept far from other institutions like schools, hospitals), etc.
Good planning doesn't try to impose a specific vision on a piece of
land; it understands that places change over time, often suddenly and
dramatically. It does, at bare minimum, try to limit things that are
unambiguously destructive to a neighborhood, like out-of-scale
development, transportation problems, etc.
But planning needs to be flexible. Desirable roportions of housing,
commercial, or industrial land don't remain constant over time. There's
no magic ratio. Making sensible choices about mixing and separating
land uses while keeping proportions flexible -- allowing conversion from
one to the other where necessary -- would be ideal. The problem is that
planning processes usually lag demand, sometimes so severely that
unintended consequences (e.g. zillions of live-work units, some of which
really shouldn't be sited where they are) erupt.
-- Daniel