I just re-read http://www.templetons.com/brad/spam/endspam.html
and find the concepts remarkably similar. Your "good guys" and
"unknown guys" correspond to my "trusted SMTP relays" and
"everyone else". I don't think your system would be acceptable
in practice since very many people have dynamic IP addresses. Yes,
I can pay more to get a static one, but I would rather pay something,
but less than the cost of a static IP address, to be able to send
email through a trusted SMTP relay server. With dynamic IP addresses,
there is no way one can get on the white list, unless the provider
gives known good customers addresses from that pool. That takes a lot
of organisation. With my system, one essentially pays to get on the
white list immediately. In my case, which I think is a good model
of how to do things, the SMTP relay server is run by the dynamic-DNS
provider (not by my ISP). He knows my IP anyway. He can (and
occasionally does) take action against anyone who abuses the system.
It works. It's cheap. And even the simplest user can get on the
white list immediately. In principle, I could switch to a different
SMTP relay server, if I wanted to (but it would have to use
authentication rather than be IP-based).