Sherry Mayo says:
Detractors of the proposed technique say problems of noise and sensitivity to mechanical defects are insurmountable and the technique could never work.
I generally speaking am leery of arguments from how well manufacturing can be done -- especially since manufacturing might someday be done perfectly using things like nanotechnology or even primitive percursors like placing your atoms for your quantum dots one by one using atomic force microscope tips (our own Tim May once proposed constructing scanning grids of such tips for such purposes.) On the other hand, I've still yet to hear any good commentary on what Shor's result really is and what sort of techniques it depends on.
ps if anyone is interested I'll try and dig out the references.
Please do Perry