Many people are worried about cloning humans and animals (more specifically people in this instance) because it may lead to a spare part culture, with clones being used as mindless meat bags, or an engineered slave race - an under class with no rights. Perhaps this could even be linked in the psyche to creating an 'elite' ruling class of the super intelligent, or strong leaders, personally I believe this would be a huge mistake, as nature thrives on diversity, and society could easily stagnate, if our leaders and general population are not replaced regularly with fresh eyes and attitudes. I believe that using clones as donor creatures is a myth in the making, science already has the technology to grow certain biological structures, so if there is to be any spare part jiggery pokery, then it would evolve into the ability to clone specific organs rather than whole individuals.
The thing that worried me about the concept of cloning whole living beings be it animal or human is that it may lead to devaluing the life of the original, leading to a never mind if he's broken, we'll just make another one.
Another factor is whether we believe in the soul or not, if so then the clone although physically identical or close to it, will be a very different individual. This can already be seen to some extent in natures clones, identical twins or other identical multiple births.
I beleive in scientific experimentation. Although many see clones primarily as a vanity or sentimental procedure, undertaken by those desperate to replace a loved pet, or see themselves almost literally live on, or possibly even nurture a new 'them', give them the advantages they feel they lacked, and live vicariously through the new improved them.
However in my view and to conclude there appears to be an innate danger that culturally, the desire to promote the idea of cloning is resonant of the social darwinist theories of the late nineteenth century. This led directly to the totalitarian ideologies of the Soviet Union and Nazi Germany. The concept of one people, a race or in the case of the Soviet Union a diversity of people all acting and thinking according to the political orthodoxy of their governments is the ultimate outcome of cloning. Essentially the underlying concepts and assumptions that creating a utopia that alleviates all human suffering is the nightmare behind these ideas.