You should read this. And here's a good quote that applies to us all:
Another aspect of the Terri Schiavo tragedy is that many people misunderstand its cause and therefore its solution. They think the problem was that Terri did not leave any written instructions about whether she wanted to be kept alive. In order to avoid any such problem in their own lives, they are now told that they have to draw up a "living will." This is both erroneous and dangerous.Exactly.
Terri's case is not about the withdrawal of life-saving medical treatment, but rather about the killing of a healthy person whose life some regarded as worthless. Terri was not dying, was not on life support, and did not have any terminal illness. Because some thought she would not want to live with her disability, they insisted on introducing the cause of death, namely, dehydration.
So what good is a living will supposed to accomplish, aside from saying, "Please don't argue about killing me, just kill me?"