I wonder if both sides of the argument are headed in the wrong direction with regards to gay marriage.
As it stands now, the states provide a one-size-fits-all social contract for marriage and many states are arguing whether or not homosexuals fall into that one-size umbrella. What most gay rights supporters believe (and I agree) is that whatever statutory rights a heterosexual couple have, a homosexual couple should also have, but I question whether or not the state should be involved in any marriages, gay or straight.
When most current statutes regarding marriage were drafted, there were very limited opportunities for women to support themselves outside of marriage and the marriage contract was the principal instrument for determining parental rights and responsibilities. The main purpose of these laws was to prevent men from abandoning their wives and children without providing a means for their support should he want out of the marriage.
Things have changed a great deal since then. Most women have as many opportunities to support themselves as men and the issue of parental rights and responsibilities have been defined in the law separately from marriage out of necessity.
The cultural and religious institution of marriage really is a matter for the individual churches to decide, not the state. If gay couples belong to a church that supports homosexual marriages, then that should be the end of it. If not, then perhaps they should join another church, or simply go without a religious blessing all together. After all, why should they support an organization which does not support them in return?
As for the more practical aspects of the marriage contract, couples can, and probably should, reach a social contract between themselves in a manner similar to other contracts without state involvement as well. Many people do this already with prenuptial agreements. It would be a simple matter of couples seeing legal council before entering into the contract to make sure their contract meets their needs. Certainly, most marriages would fall under the same contractual template, but there are many others that don't, and in either case couples should be making the choice of what their marriage contract entails individually, not following the form provided by the state.
Rather than battle over who gets to enter into these outmoded forms of marriage, I believe we should reconsider the entire arrangement so that it better suits the actual form of our culture as it exists today. If marriage indeed is a matter of choice for the individuals involved, then perhaps we should start over in our consideration of how the state gets involved, if at all. Marriage, after all, is a personal decision between two people and we shouldn't allow the state to supersede that decision.