The author's objections to marriage have been based on a few key reasons:
1) I don't want to participate in an institution that's been historically sexist and currently discriminates against my gay friends, especially considering that my partner and I couldn't have been married in some states just 40 years ago (we're miscegenators), and 2) I'm uncomfortable with the "till death do us part" rhetoric that seems to suggest that two people parting ways is an inherent failure, rather than, as is so often the case, a necessary moment of growth and change.
She also noted the tendency for people to typically backslide into stereotyped gender roles once they'd gotten legally married, a phenomenon that is less common among those cohabiting.
My response is as follows:
Register Your Car With the Government, Not Your Intimate Relationships