Interesting ideas, +Jake VK
and +Jesse McDonald
... that's probably the way things will go. I'm all for the government staying out of agreements between 2 individuals! What makes marriage a bit different than other contracts is that we have the idea of "marriage benefits" in our society. If persons A+B decide to make a contract between themselves, I as "person C" must now treat A differently (say, if I were A's employer, I must now provide addition health care to B, even though I myself had no prior relationship to B). This is really interesting!! "A+B affecting C" is the key issue around many philosophical government debates (like taxation).
Suffice to say, either laws will be changed to not reflect marital status (Jesse's argument), which is akin to saying marriage benefits will be taken away, or if "marriage" evolves to simply a contract between any two individuals (Jake's argument), then effectively marriage benefits will increase.
I think those are the main two cases... I'm not sure I'm totally happy with either outcome. Not arguing with your points, just sayin'.