In these days, when even a normally sane, down to earth guy like President Bush is indulging himself in apocalyptic rhetoric over the possibility of bird flu invading the US [you see, he wants to show us that he's forward-looking and "concerned" in the wake of Katrina] it is useful to revisit this article by Gregg Easterbrook on doomsday predictions.
In 1972, John Maddox, editor emeritus of Nature, published a prescient book called The Doomsday Syndrome. In it, Maddox argues that most apocalyptic claims are dubious, inflated, or have such a low likelihood that rational people need not think about them. Worrying about nutty or improbable threats, he adds, only distracts the political system from dangers or problems that are entirely confirmed.
Thus Bill Clinton sat in the White House wringing his hands about the preposterous sci-fi thriller The Cobra Event, in which nearly everyone in New York City drops dead from an unstoppable supergerm, when he should have been worrying about al Qaeda, a confirmed threat to New York. Thus we fret about proliferating nanobots or instant cosmic doom when we ought to be devoting our time and energy to confirmed worries like 41 million Americans without health insurance. A high-calorie, low-exertion lifestyle is far more likely to harm you than a vagrant black hole.
A little perspective, please, folks!