Some people want to take the state of the marriage business. To some extent, you can do that now. You and your partner can create custom contracts, powers of attorney, and you can even design your own ceremony, with or without religious assistance. If you have a disagreeable break-up, you don't end up in a messy divorce - just a messy contract dispute. I suppose you could also make it a provision of the contract that disputes will be resolved through private arbitration.
If there are children and you have a custody dispute, the contracts may not rule the day, because the state may want to look out for the best interests of the children or something. (Children are persons not property, and are not bound by contracts between you and your partner... at least that's my impression.)
In about 10 states, if you don't want to be regarded as "legally married," you have to be careful. These are states with Common Law Marriage. It seems that if you refer to the other person as your spouse, and tell people you're married, then the local law may view it as a state-sanctioned marriage after seven years or so. Given the states involved, only straight couples are "at risk."
Rhyme of the Day:
Just get on one knee,
And say "Contract with me."