I tend to agree, but where does a 'do not resuscitate' order or a power of attorney fit into that?

A DNR doesn't sign away your right to life, it just asks others not to take positive action to save you. A more analogous situation would be assisted suicide, which is pretty controversial. Even then, assisted suicide is seen as a benefit to the person who's going to die, and the person who assists gets paid for it. I believe a contract which says you get to kill me in exchange for paying me (either in advance or to my heirs, presumably) would be uncontroversially invalid.

I'm not sure I see the relation to powers of attorney. Are you saying that granting PoA to another person is similar to granting enforcement rights to an arbitrator?

No, I was just referring to how someone can be granted a durable power of attorney, in which case they have license to remove the grantor from life support. Anyway, I support everything you said, and just to be clear, I'm no fan of arbitration; I was mostly playing devil's advocate.

A durable power of attorney doesn't sign away your right to life. It gives someone revocable control of your life. You can withdraw that control at any time (assuming that you have the mental competence to be able to make legal decisions). There is no way to sign away your right to life, you can always take back any rights that you give someone.

I think you did a decent job playing devil's advocate, because now that you explained it a bit more, I'm not quite sure how PoAs fit into this. Maybe it's different because it's not done in exchange for something?