I just watched a program on this...and it seems very possible....I think we should hold off on such options, until we know exactly what kind of effects it can have in the long term.

without proper precautions and IF we chose to make self replicating nanotech it could be a very possible outcome I suppose, but one has to consider that once a catastrophic outcome like this is identified in theory, we usually take precautions to keep these theories from becoming realities...not to say that by avoiding one catastrophe we don't step right into another we didn't forsee that could be even worse. Who knows what could happen..consider if nanotech became a reality and then computers became sentient..there would be no need for terminators or killing machines, nanotech could slip into all of us undetected and kill us all in no time flat. Consider if nanotech were used as a weapon like this by nations. As far as I am concerned, science fiction has pretty muched shaped our current reality and continues to do so. In many books I have read (both fictional and non)the idea of grey goo is usually dealt with simply by making safeguards such as nanotech that has a limited life span and limited replicating process. I would assume we will do the same. Not to say grey goo is not a possiblility, but it's about as likely as a million other outcomes we cannot forsee.

I think that if there was the possibility of it happening, the government or the nation itself would try to put a stop to it before it happened