Radical tinkerers at work
The ecoweenies have a perpetual knicker knot because all the citizens of the USA aren't living in Bauhaus warehouses in large cities. So they have been busy legislating land use restirctions in states across the country under the guise of preventing "sprawl". Peter Whoriskey provides an interesting review of how things are working out in the Washington DC area in Density Limits Only Add To Sprawl - Large Lots Eat Up Area Countryside:

More than half of the land surrounding the nation's capital is now protected from typical suburban housing development, according to a Washington Post review of land plans in 14 counties in Virginia and Maryland. Restrictions in these "rural" areas limit home builders to no more than one house for every three acres, with several counties curtailing development even more.
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First, limiting construction to one house per three acres, or five or even 25, doesn't necessarily stop development. It just spreads it out, creating enclaves of estates in "rural" preserves, or what critics call "Gucci sprawl."
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Second, even when restrictions are severe enough to halt residential development in one place, Washington's burgeoning population continues to demand new houses, so builders simply go elsewhere, usually farther out.

So what's the result?

Recent limitations in western Loudoun County, for example, have helped push builders into West Virginia, while developers in Montgomery have migrated to Frederick and Washington counties in Maryland.

"As I drive home every day to West Virginia, I go by houses in western Loudoun that must cost $500,000 or $1 million in the rural area," said David Gillette, 39, who commutes to WorldCom in Ashburn. "We laugh because we have to drive by the snobs just to get to work. These houses are on 10-acre or 20-acre lots. Who can afford that?"
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"Rural crescent" is a misnomer for the 125 square miles that Prince William has set aside, said Chris Miller, president of the Piedmont Environmental Council, another major anti-sprawl group. "It might better be called the 'mini-estate crescent.' "

Lots more by following the link, but the bottom line is that all kinds of wackiness is going on because the benighted citizens uniformly don't want to live in DC itself and are flowing around the obstructions provided by the "antisprawl" laws.

So what's a good central planner to do?

Efforts at protecting open land grow out of a planning philosophy known as "smart growth," which holds that housing should be directed into compact, efficient nodes close to job centers. Theoretically, this reduces auto travel and land consumption while preserving outlying land in a natural state. The most frequently cited example is Portland, Ore., which maintains an urban growth boundary, outside of which building is sharply limited.

Unlike Portland, however, the Washington area has little regional land planning. More than a dozen counties independently draw growth boundaries, and the result is a regulatory patchwork.

Yep, install regional planning and prohibit building residences outside an "urban growth" boundary. But just think how much "better" it would be if they did all this planning and regulating at the national level? Now there's an issue the Democrat party can really get behind!