Almost everything in Chris MacDonald's essay1 is right. Near-term nanoscale technologies can and should be addressed with the same ethical tools appropriate for other technologies, and should not be confused with longer-term molecular manufacturing.
However, this does not mean that molecular manufacturing should be ignored. Although some prominent nanoscale technologists deny it, other scientists think it is workable and point to a growing body of scientific literature. Many are unsure, which is an appropriate scientific position.
Several artificial, nanoscale, programmable manufacturing systems have already been constructed. We do not know what range of products a nanoscale chemical system could make, but a system not much better than a ribosome could revolutionize several fields of technology. We can't rule out an integrated system capable of creating large products, perhaps even duplicate manufacturing systems. This would have major economic and other impacts, requiring planning well in advance.
Studies of molecular manufacturing,...