I ask visitors to confirm that they are human in the most stupid way possible - by typing "yes" or "y". I do this based on the assumption that (almost) nobody else does it in this exact way. So a bot written for posting comment spam won't know what to do with the "Human?" input area.

I hope it is, on average, less annoying than forcing you to register a username and a password, asking for your e-mail, asking for OpenID (which few people know about and fewer like), or giving you a CAPTCHA (those get increasingly and offensively hard for humans to solve).

Vote for death penalty for spam.