Annihilationism is one of the few doctrines that, were it true, I would immediately become an atheist (at least functionally) by default. That may seem like something of an extreme evaluation of a teaching, particularly one that deals with so speculative an issue as the eternal fate of the unrighteous following judgment. The ethical implications of annihilationism, however, are so drastic that I cannot imagine any other response.
According to annihilationists, the unrighteous are destroyed following judgment. They simply cease to exist. They are not eternally tormented in hell nor do they undergo purgative or pedagogical ordeals until they freely accept salvation. They simply cease to be. The position strikes a compromise between those who cannot violate God's justice by embracing universalism and those who cannot violate God's love by affirming an eternal, punitive hell. That is certainly a noble goal and, as an eschatological vision, it has tremendous appeal (even to me). Yet, as with all eschatological teaching, it has value only in so far as it gives meaning and evokes response in the present.
What then is the meaning conveyed on the present by annihilationism? What response should it evoke from contemporary believers? Annihiliationism declares unequivocally that the beliefs of the prevailing secular humanism are in fact quite correct with regard to the post-mortem fate of humanity and that we should therefore embrace the concomitant ethical nihilism it espouses. As striking as that conclusion may seem, it is quite easily defensible. One need only ask your standard atheist, "What happens to you after you die?" The answer, "Nothing." As far as the typical secular atheist is concerned, death represents the end of personal existence. Now, admittedly, the annihilationist adds an intermediate step towards this cessation of existence. They include a resurrection and judgment prior to unconscious oblivion, but the ultimate result is the same.
Proceed a step further and realize that the absence of life after death is the metaphysical grounds for the general affirmation of ethical relativism and, the more logically consistent, ethical nihilism. Because there is no life after death, there is no reason to live as if there is. Annihiliationism strips eschatology of its ethical power and makes it motivationally impotent. Who would fear for his eternal soul if you taught him that after he died, if he was among the unrighteous, that he would simply cease to be? If you live a reckless hedonistic lifestyle as an atheist you already believe that death marks the end of personal existence. Even if you were converted to the annihilationist position, that outlook does not change.
Ironically, even the standard Christian conception of universalism has more ethical potency than annihilationism. At least the product of righteousness here is the right to bypass the pedagogical hell. In stripping Christianity of hell, annihilationism strips the majority of the lost in the Western world of any reason to embrace the Christian ethos.
Annihilationism: more dangerous than universalism and atheism. Go figure.