Sue Everhart makes a compelling case that gay marriage could result in a wave of immigration and insurance fraud.
Anyone could just "marry" a friend and the friend would become eligible for a temporary permanent resident card and health insurance benefits. (That is not a typo: the permanent resident card expires in two years but is renewable.)
In fact it sounds like such a good idea, you have to wonder why people aren't already doing it. If fact, you could commit immigration and insurance fraud without even getting married! We should probably just eliminate insurance and immigration to eliminate the potential for fraud.