Checking out the legality of polygamy–Post Big Love

I never understood the difference in bigamy and polygamy until I went to Utah for the first time about 15 years ago.  I was reading the paper and saw that some man had been arrested for having 2 wives.  Then on the front page there was so big arrest made to a polygamist but it was for beating his daughter.  So naturally I had to give up all my pride and ask my hosts.

And yes, my hosts were all Mormons, but maybe not practicing ones.  After they laughed and carried on over my ignorance, they explained it.  Polygamist only have one state marriage as we saw in Big Love.  Barb was the legal wife.  The others, Margene and Nikki, were ecclesiastical wives.  That is not illegal.  It is taboo, however, in the official Mormon Church, otherwise known as The Church of Jesus Christ of Latter Day Saints.   Barb has been excommunicated because she was living in polygamy.  Bill, Nikki and Margene  had never been in the mainstream Mormon Church so they were  not excommunicated. 

So I got an email from a friends asking me what was the difference in living together and polygamy.  I would say there is none legally.  The legal problems of polygamy center around child abuse and statutory rape.  Amongst consenting adults,  what is the problem?   There has also been a problem with many of the polygamist men not supporting their children and costing the state lots of welfare money.  The Juniper Creek class polygamists ran in their own little world and lived by their own laws.  However, if people are living like the Hendricksons or those seen on the reality show Sister Wives, why does it concern us?

Any opinions or comments?