Due to the recent housing bubble, residences were over-built. Now many houses are empty. Isn't that a waste of resources? Perhaps residences could be built, to be "un-buildable", or "transferrable"? Perhaps apartment buildings could be built out of modules, vaguely resembling trailer-homes, that could be "stacked" and "unstacked", and moved around (from NYC to LA, say) if jobs dried up in one place, and workers moved to another. Apartment-condominium-high-rises could be built up in NYC today; then de-built, shipped to LA, and "re-stacked" there. Sort of "growable / shrinkable high-rises". In living systems, excesses are always "pruned away"; that efficiency has helped earth life survive through the ages. Building millions of homes, to suit specific styles, for a market that then evaporates, leaves trillions of dollars of "investment" idle. Building in ways that could be "un-buildable", to recycle materials, could be more economically efficient.