Cloned animals have higher rates of infection, tumor growth, and other disorders. Studies show that cloned mice live in poor health and die early, and a third of cloned calves die young and are abnormally large. Clones also tend to die mysteriously. The first cloned sheep in Australia was energetic and healthy, but that same day it died, and the autopsy couldn't find how she died.
Scientists advise against human reproductive cloning because of the dangers involved. Cloned humans could have infections or other complications, and they may have slower mental development, which could impact their intellect and mood. Animal cloning has been inefficient in the past, and people are afraid the same will go for humans.
Clones would basically be exactly like someone else, like something you would read out of a science fiction book. The cloned child would be constantly be compared to the adult whom he was cloned after. Some religions think that cloning should not be allowed, and that people should be created naturally.