I while ago, I noticed that Google Groups‘ new Beta system does not display full email addresses. Seeing as Google is probably the most popular usenet archival engine, and thus the main source of email address harvesting for spammers, I wondered how much affect the new system had on spam.
For the past week, I have posted to usenet with a real email address. It turned out to be a total of 21 messages in both alt.* hierarchy and the netscape.* hierarchy.
I didn’t get one spam message.
It just may be time for people to stop munging their email addresses on usenet. 
UPDATE: A couple of days later, I got two spam messages.