well i agree the GNR should be watched but i disagree that they should be limited. on the basis that once a society starts becoming scared of technology will stop advancing.  THAT scares me more than anything else. 

Joy states "that biological species almost never survive encounters with superior competitors" but there is something else that i wish to point out.  Humans can not comprehend anything greater than themselves.  this is the reason we cannot understand things like God and certain other things.  now on the other hand we are creating gnr's and if you tie that to the fact that we fear a robotic uprising to the point where it is its own theme in science fiction.  I feel that precautions would be set in place.

Finally look a what they predicted in the 50 about PC's that one day they might get as light as 1.5 tons.  well look where we are we have pcs that weigh less than 1lb. therefore by extension who knows where this technology will take us.

in closing i feel that it is ok to fear a thing but not to study it solely for the sake of fear is at best silly and at worst damaging to the human race.  who knows maybe the cure for cancer and thesecret of eternal life are in GNR's.  we will never know until, like pandora, we open the box of gnrs.