LKML: Alexey Zaytsev: Time to forbid non-subscribers from posting to the list? — the linux-kernel mailing list discusses list moderation as an anti-spam strategy.
Spam really sucks; anything that deals with email now has to include some set of anti-spam features because of it. The LKML has important features that mitigate against simply closing the list partially, such as being a point where bug reports are submitted — so this is a thorny issue for them.
For what it’s worth, I have written a system to further automate moderation beyond the basic features provided by Mailman and ezmlm. http://taint.org/wk/ModerateList describes this in detail; in essence, it’s a specialised mail user agent designed to moderate lists quickly and efficiently, with an outboard spam filter built in (SpamAssassin, of course, via its perl API).
I moderate about a thousand messages per week using this (last time I checked), and it takes about 30 seconds per day to do so, so it’s pretty efficient.
In other news: wow, talking to a good accountant can really mitigate complicated tax issues… phew.