I'm not an organ donor mostly because I think that some Doctor somewhere might give me up for dead since there are 3 people waiting for organs even though there is a slim chance I will live. That might not even be a bad decision on the part of the doctor (1 cripple vs 3 healthy people) but I don't want him to make that choice for me. If I'm alive and explained the situation for myself there is a good chance I would say "sure go for it, I'll be a brain dead cripple anyways" but I don't want that choice taken from me and given to some doctor with a few seconds to make a decision while he holds a knife over my still breathing body.