Better to shop in locally-run stores, even if they're "for profit". Because their profits, what with competition and the burden of paying full minimum wage, are likely not even enough to replace the carpeting before it turns the color of the parking lot.
I shop at a local store called Philly Aids Thrift (http://phillyaidsthrift.com/) whose proceeds are donated to HIV/AIDS-serving institutions in Philadelphia. Other big metropolises probably have other donation-oriented stores, too.
