Should the Emergency Department be society's health safety net?

In the US health care system, a core safety net provider has two defining characteristics: (1) either by legal mandate or explicitly adopted mission, they maintain an "open door," offering patients services regardless of their ability to pay; and (2) a substantial portion of their patients are uninsured, on Medicaid, and/or otherwise vulnerable. The hospital Emergency Department (ED), by all accounts, falls within the definition of a core safety net provider. Yet many would argue that this is a primary health care role for which the ED was not originally intended or equipped. Should the ED be society's health-care safety net? Should it be the main provider of care for the indigent? Is this placing an unbearable strain on the ED? Should it be providing primary health-care? If not, what are the alternatives?