Justin Mason sums up the timeline on this paper and various responses between the authors and the DSPAM developer. I'd put Cormack in the top 3 professors who taught computer science when I attended Waterloo.

Spam: or, 'SlashDot spam drama'. So, a few days ago, I forwarded a link to a paper I'd been sent -- it's a great paper, and I'm not just saying that because SpamAssassin did well -- it really tests some of the popular open-source spam filters comprehensively, and correctly. (The authors have 24 years of information retrieval research between them.)

The results have been pretty incendiary. ;) Here's a timeline with links, in case you were wondering where we are right now: