You wrote:
So, here are the choices:
1. Save thousands of people from having to deal with multiple spams per day,
at the cost of presenting a minor inconvenience to a few, or
2. Require thousands of people to receive and deal with spam (or to learn
all about mail filtering), in order to avoid inconveniencing a few.
Another similarity to NATs is that you don't know how many people are
behind a single (subscribed) address. For instance, I read your message
via a local news server. Of course, this means that any attempt to work
out the utility value of a filtering system must fail.
I'm perfectly happy to filter messages to this list locally. To be
frank, it takes a very small amount of my time. Surely people who want
to subscribe to this list are capable of setting up local filters?
Regards,
-leo