Actually, human cloning
may, in fact, serve to decrease the world's population
rather than add to it. Don't get me wrong; this is not a good thing.
Cloning, by nature, is merely a replication of an organism. If cloning somehow became an accepted method of reproduction in our society, we would be replicating ourselves rather than combining our genes with someone else in order to create a new organism. The thing is, we need these new organisms. We need this diversity. We need the possibility of mutation, because this is the only way humans can keep up with quickly evolving pathogens. In order to be able to adapt to future diseases and environments, we need to increase genetic diversity rather than eliminating it.
Even if we create the "perfect" human being and make many copies of it, when one clone gets sick, every clone will get sick. And, since they will get sick more easily because they lack any sort of adaptive capability, they will obviously become much less than "perfect."