04-16-2015, 03:59 AM
Stross' scariest answer to the Fermi Paradox/absence of KIII civilisations is something he calls the menace of the 'griefers'; species with an axe to grind could send out von Neumann machines designed to build Nicoll-Dyson lasers, and vapourise every life-bearing planet (or just the ones with civilisations).