Same Sex Marriage Again....
The rights conferred by marriage are not insignificant. Beyond the stories about prohibited hospital visits, losing all property when one partner dies, and tax benefits - marriage does come with a hefty bundel of rights. Lots of government benefits (social security, disability, veteran, medicare, some welfare benefits) only accrue to the spouse & children of the beneficiary. Marriage confers employer insurance benefits, maritial communication privileges, visitation rights in jails/hospitals/etc, bereavement leave, estate/gift tax exemptions, and many others.
Now all, or virtually all, of these rights can be contracted around. For example, a will can provide all the estate planning benefits marriage provides. However, this is costly and unnecessary when we have perfectly good default rules for traditional marriages, which could be applied to same-sex coupling. Additionally, it simply strikes me as unfair to force certain same-sex couples to go to this expense and give these benefits away to heterosexual couples free.
The government could create standardized domestic contracts for consenting adults which give the standard rights of marriage with the standard ways out of the contract (a divorce process with existing characteristics, like an obligation to pay child support for any children in common, equal division of assets, etc). These rights would inhere automatically to long-term relationships just like common-law marriages do now. This contract would take care of the rights function of marriage. The other function can be taken care of by churches. Churches can bless any relationship they deem appropriate with the title of "marriage" and thus bestow guilt-free sex for the religious.
Under this system, gay people get the rights they want and religious don't have to recognize same-sex marriage. Gay individuals wouldn't object unless what they really want is for the government to force the religious to recognize their relationships as legitimate (as some people suspect). The religious won't object unless their their real issue isn't religious, but simply they don't want gay people to have the same rights which straight people enjoy (as others suspect).*
Religious individuals can still believe gay relationships are wrong, and can still get someone to give them permission to have sex. Gay individuals can get the rights straight people take for granted, and the title they want. Win/win.
*I think it is important to note that gay marriage isn't the same as gay relationships. Religious disapproval of gay relationships is traditionally based on the grounds that the act of homosexual sex is prohibited. Offering these government contracts to consenting same-sex couples would not encourage more people to "turn gay," so I can't imagine it would contribute to the number of those engaging in homosexual sex.