I do think that science and scientists have an obligation to limit themselves in applying technology if there are good ethical to do so. Human cloning certainly fits into that category, IMHO.
However, Colsen certainly goes off the deepend with this one:
"Nanotechnologywhich, again, is being promoted as helping those with dread diseasesholds the dangerous potential of controlling or possibly even re-engineering human nature."
The difference here is that this is part of freewill, something that even christians feel is important. What we do with our bodies is well within our perogative. In the case of cloning or embryos there is no participation of the child or embryo in the decision making process. However, nanotechnology has the potential of increasing the life expectancy, life quality, and overall enjoyment of life for the person making the decision. Nanotech is a continuation of chemical engineering, something that has been ongoing since man made his first medicines.