> Of course, you still have to work out what you'll do with people who haven't filled out the form - like the newborn baby mentioned at the start of this thread.
It could be opt-in or opt-out for everyone else. You don't have to solve the problem perfectly to make it better than it is today.
An idea - this binary choice can be attached to combination of reaching adulthood (18 or similar) and combination of obtaining state ID / passport.
For younger, parents can choose. If somebody wants to argue about teens, they can decide themselves / be not-decided by their choice until reaching adulthood.
How it works is a form to do some other thing (for example, get a driving license) has a checkbox to donate and one to not donate, and the form is rejected as incomplete if you don't choose one or the other.
This of course means you don't have to apply a default to those people, because they've made an explicit choice already.
Of course, you still have to work out what you'll do with people who haven't filled out the form - like the newborn baby mentioned at the start of this thread.