[xtho]

To some extent that's rather a problem of a missing moderator (especially in usenet groups and mailing list mirrors). I could also understand though if some moderators simply gave up to manually mark spam posts.

[JoachimSchipper]

Usenet does quite well without moderators - not least because sensible news providers will drop spam before you see it. Google Groups doesn't.

[llimllib]

Not to mention that when you look, most of the spam originated from Google Groups.