Polygamous Montana trio applies for wedding license http://www.msn.com/en-us/news/us/polygamous-montana-trio-applies-for-wedding-license/ar-AAcriXZ
You've entered into 2 marriages simultaneously. Do you expect employers to provide benefits to two spouses? Or is one marriage going to be designated lesser marriage? Which spouse gets tax benefits? Also bringing up polygamy because gay marriage is legal is dumb. Some people are born gay, no one is born to be married to more than one person. If you want to be in a multi-person relationship then marriage isn't for you.
It's up to the employer. You either file married or not. There is no extra benefit suggested for having a 3rd spouse. Marriage is a social contract. Contracts can have more than 2 parties. The key question is who is being harmed by this kind of arrangement? As long as the 3+ are consenting adults, nobody.