Organ donation can be a dodgy subjects at times. My will would say only my family get my organs if they need them (else cremate me), because I don't want to sustain someone who destroyed their liver (for example) through alcohol abuse only to destroy my own as well. That's my greatest fear. That you can't control who the organs go to makes me weary. Someone has kidney disease, fine, my kidneys were working before I died (maybe...). And before people say 'But you'll be dead!'. I'm one of these people who believe you spend some time in some sort of afterlife before getting reincarnated. During that time I also believe you can (opt-in

) watch life as it plays out. And if I saw someone wrecking my organs, I'd be heartbroken. Call my belief system anything you like, I don't care XD .
As someone said, the opt-out option is bad for babies, since they can't, unless the mother has the right to opt them out. It could possibly scar the mother for live to learn that her stillborn is going to be opened up to salvage its organs (of course, there will be some who say 'no problem') . Me, personally, I prefer the opt-in.
Now, in life, if my brother/mum/sister (My dad's is a different blood type so I can't donate to him) needs a kidney, I'll be first in the line. Family always comes first for me.
Also, if people are living to about the 100 age, won't their organs be weakened with time and be more likely to cause problems? I'm not in the medical field, so someone will have to tell me.