WorldBeatPlanet and MacMegasite are getting hit pretty hard with comment spam. It looks like the spammers are randomly hitting articles with a low node number. To prevent it, I disabled comments on both sites for all but the most recent articles. I now see that my log is filled with errors like:
Comment: unauthorized comment submitted or comment submitted to a closed node online roulette.
I also added an input filter which prevents anonymous users from posting links in their comments.