Okay, so I give up... is there currently no effective way to discriminate newsgroup spam? My POPFile idea went pop, too. So how do we humans recognize the spammers, then, and how do we teach that to Newsbin and other software?
In the short term, what about a poster whitelist, as opposed to a poster lockout? This could be implemented manually or automagically through some intelligent pattern-matching. Obviously Newsbin can't analyze binaries themselves to determine intent, but the habits of posters themselves over even a short periods of time can clearly identify them. That may not be true of all newsgroups, but it is certainly true of some.
At least in some binaries newsgroups, there is a readily identifiable minority of regulars, who are clearly NOT spammers: they post frequently and/or in large amounts, and almost universally avoid spammy words in subjects. Then there's the rest, who post too infrequently or don't post enough to make their motives clear. In such newsgroups, even the formerly innocent requests for binary ID are now an invitation to spam, so simple word or phrase matching can't really vet even those infrequent posters. Still, the best and brightest of these groups stand out sharply. If we humans are able to pick them out with ease, why can't an algorithm?
If Newsbin were to log the quantity, type, quality, and frequency of what each poster submits over some period of time, clear patterns would begin to emerge, and those patterns would enable identifying at least the best that the newsgroup had to offer. If applied too rigidly, it would exclude new or infrequent but legit posters, but still the method is sound. It's sound because it's exactly what many of us are doing almost unconsciously already to make those same judgements ourselves.
I'm no longer enough of a programmer to express something like this process in contemporary code myself, but even I can visualize bits of the algorithm as I write this. I'm sure that one or a few good coders could do the idea justice. If that were implemented in Newsbin, it would place it an order of magnitude past its competition (and you know some spies are probably reading this, too).