As each individual news article is piped through a relatively small
number of servers in the "core" of the distribution system, it becomes
relatively easy to blacklist known offenders. That is, if they are
recognizable as such. This is where the authentication comes in. The
tricky part is optimizing the time/difficulty it takes to blacklist vs
that of obtaining a new identity.
Even though this is a good point, I'd prefer to stay off the discussion of
authentication, because the proposal need not depend on it, as you point out
Also note that with usenet news, unlike email, it is possible to remove
spam that has entered the system, limiting the audience that sees the
message and thus the effectiveness of spamming.
Also bear in mind my point that the whole point of moving legitimate bulk
messaging to "pull" is so that spam can be dealt with unambiguously by
enforcers on bulk email. So spam (all remaining *BE) gets reduced by the
paradigm switch to "pull" for legitimate bulk messaging. Since I assume
mailing lists would still use email as incoming source primarily, then incoming
spam is reduced. You could certainly switch to a authenticated interface (e.g.
https web page) for incoming mailing list traffic, but I think that is
unnecessary to my proposal.
Also remember that some portion of legitimate bulk messaging is legitimate
(meaning that receivers want it) corporate bulk mailings. They would also be
forced to the "pull" paradigm, but not their normal single messaging, such as
the receipt for what you buy on Amazon, only their bulk email.