I have installed the 'honeytrap' at http://www.raditha.com/specimenfederation.php (yep it looks like a terms of use page but the bots will see it differently).
Getting back to the http:BL plugin; what it does is prevent known spammers and email address harvesters from seeing your page. But this is not ideal, sometimes there may be rare cases of mistaken identity (after all Most ISPs asign dynamic IPs), It would perhaps be better to allow everyone (even IP addresses that are listed in project honey pot) to visit the site and read the comments but to prevent them from posting new comments. Maybe there is room for another plugin ....
I always talk of writing WP plugins but so far, I have written only one....