I have wondered many a times, what are your rights and duties as a friend? Legally, I dont think a friend has any privilege in over a stranger. Sad, but true. Even some not so well meaninged relatives have privileges/rules conferred by the law.
So we dont have a legally bounded duty for anything for a friend.
So is is right to assume certain things for friends and take decisions on behalf of them? On very small issues, I am sure friends wont mind. But what about bigger issues? What if a major decision has to be taken and no family member is available at the moment? How does it work then with no one really listening to a friend of the person in case of major medical emergencies or such scenarios.