Justin Davidson: Why glass towers are bad for city life -- and what we need instead

There's a creepy transformation taking over our cities, says architecture critic Justin Davidson. From Houston, Texas to Guangzhou, China, shiny towers of concrete and steel covered with glass are cropping up like an invasive species. Rethink your city's anatomy as Davidson explains how the exteriors of building shape the urban experience -- and what we lose when architects stop using the full range of available materials.