just wanted to add... a lot of polygamous families are supported by the welfare system. They get food stamps & govt aid. The man legally marries the first wife, but the rest of the wives are considered "single moms" when they have children, and qualify for welfare benefits. Your tax dollars hard at work. Government sposored child abuse - so much for "family values."
An interesting book on the subject is "Under the Banner of Heaven" which is about fundamentalist mormons who practice polygamy. Makes the Witnesses seem almost normal by comparison.