It seems bizarre that a hospitalized patient could suicide by not drinking without the staff being complicit.

I'm sure they are, but I don't think the situation is that bizarre. I mean, isn't that exactly how Terry Schiavo's body died? The husband had food & water withdrawn, and the hospital staff was complicit in letting it die.

Reading http://en.wikipedia.org/wiki/Terminal_dehydration#Voluntary the legal basis is actually a little weird. Apparently putting in the IV drip without consent would constitute assault! And this right to refuse treatment has been upheld at the Supreme Court. I am also surprised to read this:

One survey of hospice nurses in Oregon (where physician-assisted suicide is legal) found that nearly twice as many had cared for patients who chose voluntary refusal of food and fluids to hasten death as had cared for patients who chose physician-assisted suicide.[13] They also rated fasting and dehydration as causing less suffering and pain and being more peaceful than physician-assisted suicide.[14] There can be a fine line between terminal sedation that results in death by dehydration and euthanasia.[15] Studies have shown that for terminally ill patients who choose to die, deaths by terminal dehydration are generally peaceful, and not associated with suffering, when supplemented with adequate pain medication.[16][17][18][19][20][21]

I had thought dehydration was a terrible way to die. I guess not.