I don't know if it's the most popular in the world, but actually it wouldn't surprise me. Even in England last year, Mohammed placed at #22: more frequent than Ryan or Dylan or Alexander. And the various spellings combined (Muhammad is at #44, Mohammad at #69) it's more popular than the stats suggest. After all, Islam is the fastest-growing religion in the world.
I don't know anything about Mormons using it :-s
We have, in fact, two kinds of morality side by side: one which we preach but do not practice, and another which we practice but seldom preach. - BertrandRussell