Oh and there are those baha'i people too.
Jakko, I'm gonna have to disagree with you regarding what marriage essentially is. Correct me if I'm wrong, but your saying that marriage is under the purview of christianity, and civil unions are what anyone else can have? Well according to how I, and the dictionary http://dictionary.reference.com/browse/marriage , perceive it, marriage is simply the pledge of two peoples to spend their lives together as a couple, which normally involves either religious or legal affirmation.
If christians want to segregate certain people and not marry them, then that's their choice, I agree. However my problem is that marriage conducted under the auspices of christian ceremony is, at least seemingly to me, considered the normal way to go about things. My point, is that if christianty does wish to single these people out, this control (perhaps wrongly percieved on my account) of marriage should be removed, and replaced with a ceremony everybit as authentic and credible, but conducted by the state.