Jeff Atwood points out several problems with using blacklists (specifically Akismet) to prevent comment spam. He makes the following point: The core problem is relying on a single method of defense against spam. Absolutely. Subtext employs several measures against comment spam, mostly of a heuristic nature. The latest release adds Akismet support as well as Visible and Invisible CAPTCHA. The funny thing about CAPTCHA and especially Invisible CAPTCHA is the number of people who claim it won’t work and is broken. As Jeff points out, this may be true among researchers, but it is not the case in the wild. However...