Love and Marriage

So, my good friend Matt and I have been having some back-and-forth blogging on the subject of marriage and dating.  Although I don't agree with all of his points, I thought he had a very interesting one:  

Marriage is a lot more than a piece of paper, double income and easily accessible sex. Our culture has just tried to dilute it down to that.

Interesting point, Matthew (who, for the record, is married).

This raises quite a few questions in my mind - what are the pros of being married (as opposed to living with someone or being in a serious relationship - not as opposed to being single)?  Have we lost sight of these pros?  Do these pros outweigh the potential cons of being married?

I'll try to weigh in my opinions...after I get some feedback.  :)