Anyone who gets married without being aware of these things is an idiot. And anyone who would marry someone who they didn't trust with this power is an idiot squared.
Marriage is a unique institution in our society. It is considered to be so solemn, private and intimate that courts may not inquire as to the private communications between husband and wife. No such "parental privelege" exists. Ironically, it is many of the same people who have championed the uniqueness and sanctity of the marital relationship vis a vis same sex marriages who now are howling that really it ought not to be the spouse who makes life-and-death decisions for those unable to make their own decisions, but the parents.
It's a funny world.
It is doubtful that people realize that they are granting near arbitrary authority to deprive a spouse of dental care, parental visitation, rehabilitative therapy, withdrawal of nourishment/hydration if the patient's condition is disputed etc.
Michael Schiavo even thought he had the discretion to allow his wife to die of a urinary tract infection in 1993 [soon after the malpractice award]. Amazingly, Florida law actually prohibited that.
My wife and I are drafting documents to see to such life or death authority does not solely rest on each other's shoulders. [I shall post a version of it when it is done.] We are humble enough to know that such a responsibility is beyond our respective capabilities.
A condemned criminal's life does not rest in the hands of any singular individual. Neither should it be the case for an innocent disabled person.