Tossing another two cents into the Bean/Horwitz debate below:

My question in my initial comment was "If the State of Illinois were to declare interracial marriages invalid, should the university roll over and refuse to grant benefits to interracial couples?" I haven't seen an answer to that yet.

And on polygamy: I certainly think polygamy should be legal (regardless of whether it's likely to be stable and regardless or whether it's likely to win public acceptance). But there is certainly an argument for same-sex marriage benefits that isn't there for polygamous-marriage benefits: namely equal treatment. If a heterosexual couple can get certain benefits, it's only fair that a same-sex couple be offered equal benefits. But if there's no limit to how many spouses I can bring to the table, all eligible for benefits, than I am putting a greater burden on the financial resources of my employer. The employer is entitled to draw a reasonable limit on the number of spouses to be supported -- but I don't see how the gender of the spouses is relevant. (In a sense this isn't an argument for denying benefits to polygamous partnerships at all. The employer can say: each employee can get X amount of benefits for the sum total of all his/her spouses, be that number one or more than one ....)