I usually don't bother with the gay debates, partially because other adults' bedroom activity doesn't interest me and partially because taking a position on the issue can sometimes lead to name calling nastiness.
But gay marriage is a little more serious. To me it seems intuitive that gays--or first cousins--or aunts and uncles, or polygamists, or adults and children, should not have the right to marry. It's also intuitive that awarding gays the rights of full marriage will cause a tilting of the slope until it becomes slippery, even if there aren't many skaters on it. Marriage is in enough trouble as it is.
To me the institution provides the basic framework for a productive society despite the ills (perhaps we've made divorce too easy). It's also intuitive that all other things being equal, children will do better with a mother and father. This isn't rocket science.
The other side might ask whether my neighbor's gay marriage affects mine? The answer is no, but does theirs, and thousands of others, affect society at large over the long term? I don't think we know that yet. Sometimes the good of society has to outweigh the rights of individuals, which is why most states prohibit cousins from marrying now.
So that's my piece on the matter. And with that I disagree with Tom Maguire's rather nasty call-out of Rod Dreher as to the Iowa decision, bashing him for something he didn't even say. Personally I think it WILL get harder for Christians--and MUSLIMS alike--and atheists who believe in the laws of nature--to freely express their dissent on this issue if gays gain the acceptance they want by a grant of full marriage instead of civil unions.