[zanny]

The problem is that, while there is now a large stock of massively oversized residences to have large families occupy, said residences are built around an expectation of extravagance that makes them far removed from commercial, business, or even other residential areas. They are isolated by design and extraordinarily expensive to maintain both publicly and privately.

If that square footage was simply placed somewhere with reasonable local access to services it would be less concerning how disastrous the housing and property markets are, but the McMansions are going to enter total obsolescence and abandonment when their current residents want to downsize and nobody can afford to live there.