Abstract Appeal -- The Terri Schiavo Information Page is one of the few unbiased resources on the Internet that describes this tragic case. There are many sad components to this case, but from my perspective, the lesson here is that everyone should fill out a Health Care Proxy and a Living Will. It seems that she had made her feelings clear to her husband, but she had never done so in writing.
An example: you can find the New York Health Care Proxy (pdf) on New York's health department website. This document on the NYSDOH website actually performs both functions - as it defines who is the proxy - and then it provides a space to guide the proxy:
"Putting things in writing is safer than simply speaking to people, but neither method is as effective as appointing someone to decide for you. It is often hard for people to know in advance what will happen to them or what their medical needs will be in the future. If you choose someone to make decisions for you, that person can talk to your doctor and make decisions that they believe you would have wanted or that are best for you, when needed. If you appoint someone and also leave instructions about treatment in a Living Will, in the space provided on the Health Care Proxy form itself, or in some other manner, the person you select can use these instructions as guidance to make the right decision for you."
"In some other manner" suggests to this non-lawyer (but I know one pretty well!) that any written communication would be helpful. An e-mail, a letter .. anything. For the record .. if I end up like Terry for some horrible reason ... let me go.