Its not about owning anybody V. Its about a committment, trust, and communication. When you get married, you should do so because you love the person. Not in the way of a regular friend, but in the way of somebody "special". Theres only going to be one person in your life like that (and for some of you 4 or 5). This isnt just hanging out with your buddy, and having that kind of relationship where you can screw her, then she goes out and screws other guys. You can do that when you are single. Why in any way would you want to get married if it didn't mean a monogomous relationship? Why do it at all if you believe that? I really dont see the point.
The idea of marriage has purpose, and I think that marriage is something special that should be respected. If one cannot respect it, then they should not desecrate it by violating the very principals of it. Of which are: committment, trust, love and communication (and more).
Marriage is not, and should not, be some that is whimsical and done "just because". It destroys the meaning of it to have people that abuse it like that. Co-habitate and cheat all you want, and be honest to your partner and the world about the situation.