Martin Rees is misrepresented 4:04 in. What Rees actually said was:
the odds are no better than 50-50 that our present civilisation on Earth will survive to the end of the present century without a serious setback'
...whatever a "serious setback" is supposed to mean.
Do you have a reference for that? My copy of Our Final Hour contains the same sentence minus "without a serious setback".
http://vimeo.com/22099396
What do people think of this, from a Bayesian perspective?
It is a talk given to the Oxford Transhumanists. Their previous speaker was Eliezer Yudkowsky. Audio version and past talks here: http://groupspaces.com/oxfordtranshumanists/pages/past-talks