Space expansion can solve all nanotechnology abuse and accident
problems.

Assuming more than one space colony expanding out in space in
different directions, and assuming one or more has a runaway nano-
assembler problem; well, since the nano-assemblers are confined to
the given spaceship, they won't spread to the other space colonies
since there is 'space' between them. What's more, space radiation
and the nano-assemblers eating on each other will eventually make
that mass harmless as far as any further nano-assemblers continueing
to run amok. Almost any collision with massive rocky and even ice
bodies throughout the universe will result in extermination of the
lunp of runaway nano-assemblers. Assuming that maybe general space
conditions don't finish the job actually leads to how space
expansion of many space colonies overcomes nano-terrorism.

A given space colony with nanotechnologies will have the means to
detect particles of all types really from general atoms and
molecules radio astronomers have been studying for decades now.
They should be able to detect the odd signature of a stray nano-
assembler out in space. A stray nano-assembler out in space should
raise a few eyebrows anyways; if they don't, it's their fault for
not allowing thinking to occur. Assuming a given space colony's
intellect hasn't been dimmed by irrationalists to the point of
ignoring outerspace, they have various means of defending oneself
from stray nano-assemblers(possibly nano-terrorism); they can use
nuclear, laser, or an intense radiation shield; or even Utility-fog.

Definding against nano-terrorism(at least from those outside a given
space-colony) has actually been delt with already. Space colonies
expanding away from one another out in space has one more benefit
for overcoming nanotechnology accidents. Basically, out in space,
nanotechnological accidents can be almost 100% overcome by making
nano-manufacturing ejectable out into space; if a nano-assembler
gets out of control, then detectors can tell say the rocket that the
nano-manufacturing unit is on to rocket off out in space; from
there, one can nuke, laser it; or, one could have the grey-goo mass
pointed at a local star(whether a nuclear burning star, or a newtron
or black hole!).

Seems to me that space expansion is the only way to make our nano-
future safe as far as I can tell. I could go on and on about the
other benefits of human expansion out into space like overcoming
human's social propensity for becoming dogmatic which I would think
has been proven throughout human written history as a danger to
humanity . . . since after all, Humanity is the technologically
dependent species. Out in space, if a given space colony gets
ideologically split, they can split and go their separate ways;
those who are wrong with run into problems with themselves like the
way the Catholic Chrisitan church went through three bloody
revolutions during the dark ages.