From http://www.alcor.org/cryomyths.html#myth3

The purpose of cryonics is to save the lives of living people, not inter the bodies of dead people. Death is a neurological process that begins after the heart stops. A stopped heart only causes death if nothing is done when the heart stops. Cryonics proposes to do something. In the words of a mainstream critical care expert writing for the American College of Surgeons, "In this era of critical care, death is more a process than an event.... A prognosis of death...cannot serve as a diagnosis."

I don't feel that I understand this fully. Is there a point in this "process" from which we've already brought people back, or is this all just conjecture?