Yes, this is something we need to think about. The US has a patchwork of tolerance as things stand; some states allow marriage without regard to gender of the participants, while most don't. Some recognise out-of-state same-sex marriages, some don't. And then there's California, with its horrible mishmash of things that are still being decided in court.
Now, personally, I regard the various same-sex married couples I know as legitimately married. They've made a committment, just like I have, and that deserves respect. That they don't reap the tax advantages I do from the Federal authorities is a travesty. That said, marriages don't always last. What happens when a same-sex married couple decides they need a divorce?
If the state certifies such marriages, it shouldn't be a problem. But what if the state recognises such marriages, but doesn't perform them? Is it obliged to provide for divorce of marriages it doesn't perform?
And what if the state doesn't even recognise the marriage? I dread to think of the problems which could arise should the respondents accept an answer of "you were never really married in the first place", and then attempt to re-marry.
This is a problem that deserves much more attention than the "none" it's recieved so far.