Clones are evil! At least, that's what we're often told. Popular media generally portrays clones in a negative light, such as the many copies of anthropomorphic human-hunting Cylons in Battlestar Galactica or the mindlessly obedient squadrons of emperial soldiers in Star Wars. In some academic circles, bioconservatives clamor about the immorality of cloning, appealing mostly to fear of the unknown correlated with (presumably temporary) technical limitations.
So far as I can tell, clones aren't necessarily so evil. In fact, I've known several clones, and they've all appeared to be quite as good as any other persons I've encountered. Technically, the clones to which I'm referring are more generally described as identical twins, and there are a few differences between them that I'd like to explore briefly here.
First, identical twins result from natural DNA duplication, whereas clones result from artificial DNA duplication. Cloning is currently accomplished via transfer of a donor cell nucleus to an egg that no longer contains its original nucleus.
Second, although both identical twins and clones are the result of DNA duplication, identical twins have MORE in common than do clones, given current cloning processes. While clones have duplicated DNA in common, identical twins also have the an egg and gestational environment in common. To whatever extent the egg and gestational environment affect development, identical twins should tend toward greater resemblance than should clones.
Third, current cloning processes tend to result in imperfections that generally manifest themselves negatively as clones mature.
I consider the first difference between identical twins and clones to have, in itself, no greater moral implication than the difference between natural conception and in vitro fertilization. I mention "in itself" because I can imagine many ways in which the components for the cloning process (such as the eggs) might be harvested in oppressive ways. However, whether the process is natural or artificial does not play into the morality of the process, so far as I am concerned -- and most persons living in the modern world would have a hard time disagreeing without hypocrisy.
The second difference indicates that there is no reason to fear that clones might somehow attain to something less than a unique identity. We should expect clones to be at least as unique as identical twins, who don't appear to be excessively concerned that they share duplicated DNA with another person. While I can imagine some twins wishing away their twinhood, no twin I've ever met has had anything less than positive to say about the value of her (or his) relationship with her (or his) twin.
Finally, regarding the third difference between identical twins and clones, I do see this as an ethical concern, although not an insurmountable one. Until cloning is demonstrated to pose no greater health risk than alternative conception processes, it should not be used to conceive humans.
In summary, while we should be concerned about the morality of the details of the cloning process, the general phenomenon should not be of so great concern as it appears to be for some persons. I suspect that, in time, the fear of clones will subside as the technical process improves, the unknowns dissipate, and the novelty wears away.