My issues with cloning are:
At what point is a developing human embryo imbued with a "soul" (or the essence that makes each of us unique)? Until this is truly defined and identified, we, as both a society and individuals, have no right to tamper with that life.
Also, I think that with cloning, we will develop second class citizens, those with the rights to those inalienable rights of life, liberty and the pursuit of happiness (to quote a "minor"
document) and those that will never have those rights. Doesn't that undermine a major portion of the basis of our (The United States of America) nation?
Until both of these issues are addressed in such a way that protects the rights (both the secular and religious) of all involved, we really should steer clear of this area. The ability/techniques of cloning will still be there, waiting for discovery or development, after these issues have been resolved. Science and scientists need to understand that their developments do not occur in a tidy little vacuum and these developments can (and generally do) have serious social, religious and political ramifications that need to be addressed. We should not take the stance of "Lets do it and figure out the ramifications and how to deal with them later", that is poor planning and can end in disaster.
My final point is: Would you knowingly end another human being's life to preserve your own life, that was not directly being threatend by that other human being?