I'm still making my way through Firefly/Serenity-related threads, so perhaps this has been mentioned before. Did anyone else notice the registration numbers on the crashed rescue ship on Miranda?
It was C-57D, the same as the starship in Forbidden Planet. (The number is also seen on a shuttle that Jayne inspects—probably a scooter from the rescue ship.) Miranda, the name of the planet, was Prospero's daughter in Shakespeare's The Tempest, the basis for Forbidden Planet.
The message in Forbidden Planet is that even after a million years of civilization, the lost Krell were still "human" at heart. The "ego" and "super ego" of the Krell had advanced, but the "id" still lurked inside. And the Krell technology empowered that inner savage.
In Serenity the social engineering carried out by the Alliance planners released a similar "id monster"—the Reavers. The chemicals added to the air processors stripped the unwitting populace of all passion and will-to-live. They all died of apathy. The chemicals had the opposite effect on a tiny percentage of the population—it stripped away the veneer of civilization and left nothing but savagery.
Mal gives a pep talk to his crew where he says, "They'll swing back to the belief that they can make people...better. And I do not hold to that." Yin yang. Mal knows that people cannot be good without the struggle against evil, a theme brilliantly executed in the Star Trek episode "The Enemy Within." (Kirk learns that his strength of command comes from the savage inside, properly tempered by the intelligence and compassion of his "good" side.)