In my experience, atheists tend to agree with Den Beste -- the cessation of self is not in fact the worst of all possible outcomes. There are things that are more important than the continuation of existence. Atheists tend to (tend to, I say; there are a lot of individuals spread pretty evenly along the spectrum) also agree that a person has the right to choose when to end their existence.

For some reason, many of the religious people with whom I've spoken about the subject disagree -- they believe that we should never help a person die, and that it is in fact a sin, or at least a moral wrong (in the case that there is a difference), to choose to stop existing.

This confuses me. Logically, it would seem to be the people who have something else to look forward to who would be the least interested in preserving their lives here at all costs, and the ones who expect oblivion, who believe any goals they have must be accomplished prior to death or not at all, who would cling to life with incredible fierceness, who would hold it actually evil to end another person's suffering.

I think the difference actually lies in the existential beliefs most atheists end up embracing: as Den Beste notes, "simply trying to live as long as possible is not the goal [we've] selected". For someone who believes that life is intrinsically meaningful, that meaning is created and assigned by some higher power, then merely living as long as possible extends the meaningfulness of their life[1]. In fact, taking their own life -- or someone else taking theirs -- actually possibly interferes with the great cosmic meaning of their life, since they can't know whether the meaning assigned by that higher power has been accomplished yet or not. To someone forced to create their own meaning, to decide when and where meaning enters their lives, it also ends up being their decision as to how they make their life more meaningful, and they are much more aware of how complete their goals are, how soon they can call it quits, so to speak. Thus they are much more emotionally (and rationally) ready to end their own life, when they feel that the remaining suffering in their life outweighs the remaining good they can -- or want to -- do. Meanwhile the religious person must continue to hold out hope, even in the extremes of pain and a damaged, dying body, because they can never make a judgement about the meaning yet to come in their lives, can never guarantee that they wouldn't have been saved at the last moment because their work (as assigned by a higher power) was done.

As an atheist, I have to end this by noting that I do agree with Den Beste; I decided a long time ago that some things were more important than continued life. If I were in some sort of accident, and I were to spend the rest of my life paralyzed so thoroughly that I couldn't even communicate with anyone else, for instance, I would seek to end my own life. At that point, the costs of my continued existence -- to myself, to my wife, to the world at large -- would in my opinion exceed the benefits. I don't mean economic benefits only -- though the cost of supporting me would clearly be prohibitive. I mean emotional benefits. How much could it benefit my wife to have a husband who could not move, could not talk to her, comfort her, laugh at her jokes, who could not even communicate that he loved her, or indicate that he knew she loved him? At that point, my death -- while obviously a hardship for her -- would also free her to grieve properly, to move on with her life free of the anchor I would have become. I don't mean this to be some sort of heroic decision, either; it's a simple decision based on what my life would be worth to me, what I felt I could still accomplish, and how my life would affect both my happiness and the happiness of people I cared about.

[1]: Obviously I don't mean to imply that religious people are incapable of making informed decisions about pain, suffering, or meaningfulness. Many religious people every day knowingly make decisions that make their lives more or less meaningful, in whatever sense of the word that applies to anyone, atheist or not. My point is more about the ability (or lack thereof) that a religious person has to make a cost/benefit decision as to their (or a loved one's) continued existence.