Nothing, but who cares? As I noted before, the only financial advantage they'd get is being able to file as "married filing jointly." Most of the benefits of marriage -- ability to make medical decisions, rights of survivorship, joint property rights -- are either irrelevant or unattractive to scammers.

And the actions of scammers are hardly a reason to deny gays the ability to marry. Right now, opposite-sex friends can do exactly what you fear. Should we outlaw straight marriage because of it?

__________________
Man up.