I would happily support the privilege of people to opt out of organ donations, as long as they are willing to irrevocably forego being the beneficiaries of an organ transplant.
Or hell, at that point, I'd happily make it opt-in.
I'm not so sure about that. I can easily imagine misguided parents angrily opting their children out - it would be cruel to deny transplant to these kids just because their parents are, well, not so bright.
I disagree. If there's an available organ and a recipient in need, it should be used regardless of the recipient's donor status. Why waste the chance to save a life? Donated organs aren't good for very long.
It's fine to use donor status as a tie-breaker if multiple recipients are in contention.
EDIT: Plus the other reply about children.
There's nearly always a shortage of organs, and people who opt out are contributing to this shortage. If you want donor status to be a tie-breaker, it will, in practice, be a ban.