I know the common argument for this practice is that it supposedly hurts much less when you're an infant. Well, to be more precise, it hurts just the same, the only difference is that the child won't remember it. I don't know whether it's reason enough. I think the child should be able to decide whether they want their ears pierced or not.
Why on Earth would parents want to pierce the ears of their babies? What's the rush? Is your baby going to pick out a matching necklace and ring to wear to the daycare that day in order to out-fashion the other kids there? Babies are about eating, sleeping and pooping until about age two. Earrings are fashion statements, plain and simple. Kids can wait until age 5 to 10 in order to get ears pierced if they so choose.