R. R. Reno on conservatism and gay marriage :

Redefinition of marriage to allow same-sex unions undermines the proper separation of cultural and governmental power that is so important for a liberal regime. Marriage is an institution as fundamental as religion and morality. It is more primitive and ancient than anything resembling organized government.

Also today, Laura Mitchell explains the transaction costs of cohabitation :
What happens when a couple lives together before they get married? These transaction costs are magnified to such an extent that it’s nearly impossible just to walk away. Doubts about the relationship are swept aside because to address them would mean to look on Craigslist for a new apartment and furniture.