Much of the more active end of the present transhumanist community is very concerned with existential risk on a grand scale: the Singularity Institute, the Lifeboat Foundation, the Center for Responsible Nanotechnology, and so forth. It doesn't hurt to have some people thinking about the end of the world - it seems like a good plan, given the balance of risk and odds as we presently understand it. A tiny risk, gargantuan consequences, a lot of people in the world, and just a few thinking meaningfully about how it might all fall into the pit. A sort of inverse Pascal's Wager, if you like.
As a fraction of the community of folk focused seriously on advancing technology and pushing out the horizons of what is considered possible - as opposed to those who are short-sighted or merely along for the ride - I think that the existential analysts are somewhat overweighted, however. There are too many people finding reasons to say "hold up a moment here" and too few with the pedal floored to the metal.
I'm of the opinion that "hold up a moment here" is a poison of this age. It's in the air, a toxin that seems right at home in the cultural background mix of NIMBY, death by precautionary principle, environmentalist Malthusianism, bioethicists whose funding depends on finding roadblocks, and comfortable, wrong-headed assumptions that next year will look just like last year. Vast numbers of people are trapped in the illusionary moment, fighting every change in an age of change - and there are so many of them that some little part of their attitudes inevitably seeps into every part of the grand multi-threaded conversation that is our culture. Even those parts that are ostensibly focused on achieving progress.
The precautionary principle is a distillation of inaction forced by excessive caution. More extreme expressions of the precautionary principle have been seized upon and promoted by all sorts of opponents of progress because they represent a halt to all progress: no advance is ever risk-free. Demanding - and attempting to enforce - risk free progress is one and the same with halting the engine of science and technology. Many foolish people want just this, sadly, and would condemn every living person to suffer and die from degenerative aging to achieve their ends.
Sadly, the popularity of extreme expressions of the precautionary principle obscure the high costs of adhering to even moderate versions. If you attach a ball and chain to those working on medical progress, medical progress will be slow. How can anyone advocate slowing down progress in the face of 100,000 deaths each and every day? Yet this seems to be the mainstream position; those who do not contribute to getting the work done have largely fallen down the rabbit hole of doing nothing but throwing roadblocks in the path ahead. Great job, you all - I hope you manage to live with yourselves if scientists create working anti-aging medicine within our lifetime despite your efforts. If science is held back well enough ... well, then we all age, suffer and die. Well done. Applause. A pity you won't be there to receive the gratitude of the masses - who won't be there either.
While this all takes place, hovering over us all is the grand sword: that in fifty years, barring a big fat revolution in the entire ethos and strategic direction of the life science community, we're all dead or dying. There's your existential risk. A very large "certainly dead, all of us, unless we do something" existential risk. Not a small or unknowable or yet to be quantified risk, but a certainty ... unless we act to develop rejuvenation biotechnology.
So we can floor the pedal, or we can talk about why it's a terrible idea to floor the pedal without doing all sorts of other things first. I know which approach I think will dig us out of the hole we're in - and it's not the one that involves moving ahead slowly.