I was IMing with a friend about inbreeding depression and came across a map which shows the laws regarding cousin marriage in the United States....
(nothing else really jumps out at me) Of course the whole cousin marriage issue isn't as "hot button" as same-sex marriage. I assume cousins who marry in a state where it is legal have their marriage recognized in states where it isn't? It will be interesting if gay marriage becomes much more common if cousin marriage comes up too since it is much more common internationally.