Billy Brown, <email@example.com>, writes:
> I hereby challenge anyone to come up with a disaster, natural or
> artificial, that could reasonably be expected to render an advanced
> spacefaring species completely extinct.
How about a computer virus? Let it have a long latency period before it flares into destructive mode, so that it spreads everywhere. Then let the people be such that they can't live without computers. Maybe they are cyborgs or something. When the virus flares, they all die.
You could probably do the same thing with a biological virus, except without nanotech it is harder to create something with the necessary flexibility.