So virtually overnight, there's a billion copies of some AI in robot
bodies, of unknown internal thought processes and motivations, and
probably thousands of copies embodied as super-AIs.  So the society
ends up with a huge monoculture of poorly understood beings, who can
easily copy themselves into commodity hardware, and some who can think
and learn just as well and very much faster than any human.

That's not an automatic recipe for disaster, but it's fertile ground
for one.

, but the
assumption that strong AI can inhabit cheap hardware as soon as it is
developed does seem to be a common theme across a lot of science
fiction, both optimistic and horribly grim.