Comment spam
Don Box: To date, the few times I've wanted comments, I've pointed people over to Sam's place and let the peanut gallery operate on Sam's bandwidth dime. I think this time around I'll do it mainly because I want to experiment with some anti-troll/anti-spam ideas.
Comment spam has gone from a curiosity to an irritant to an amusement of mine. Why an amusement? It is fun seeing greedy spammers who can't limit themselves to two consecutive comments earn a 24 hour ban on posts from their ip address and on posts which contain the url that they are trying to pimp. This ban is later upgraded to 72 hours once I manually verify that the comments are in fact spam.
Today somebody tried to post ten times from a variety of ip addresses before they finally gave up. The next step may be to automate the removal of the initial two comments on such attempts, making this process totally painless on my part.
The best solution I have found to date to trolls is trackback and pingback. It is amusing to me how many people who get sanctimonious about their rights to my bandwidth go silent when I suggest that they post their comments on their weblog.
If you do implement comments, one thing I suggest is that each comment should have a permalink. Next on my list would be feeds for, and search over, comments.