Dave that post about SpamKarma is almost 3 years old (3/27/2005) and is with wp version 1.5, wp is up to version 2.3.3 now.
I don't have any problem with it slowing down my blogs at all.
SK
I had not realized that Spam Karma had created a fulltext index of the comments table and I had not removed that index. Adding to the problem was the feature of Wordpress 1.5 that stores all spam comments. The comment fulltext index had grown to over 50 megs in size (with over 25000 spam comments plus the few thousand legit ones). All of this resulted in every mysql query taking more than one second to execute.
SpamKarma doesn't create a fulltext index anymore nor does WP store all the spam comments anymore.