I'm watching Lifting the Veil of Polygamy. It talks about how Joseph Smith (and most of the other presidents of the Church of Latter-Day Saints) practiced 'polygamy' (plural marriage). In fact, some of his important writings state that–going along with the "As we are, God once was; and as God is, Man shall one day become"-dogma–goes about justifying/fundamentalizing polygamy (nearly making it a tenet as necessary as virginity!).

I can see where he was going with "you cannot become gods without being polygamist." Having lots of people depending upon you, hanging on your every word and devoting themselves to you gives you a Holy high—the feeling that you can do no wrong. (Of course, that doesn't excuse any of your wrongdoing; it just removes a little bit of the guilt that keeps you from doing what you need to do to serve The One Truth.)

This is of course a modern viewpoint; in a time when there are various "protections" against pregnancy (because each "child" is an additional task—a yoke that is too heavy a burden to bear with an 'in your spare-time'-focus).

While the man is single (i.e. while no woman he's seeing has a child), he can have as many live-in girlfriends as he can handle. But when he decides to live forever, he chooses one woman (who also chooses him), and marries her-and-only-her.