My site is being protected from comment spam by the Mollom system. I like that it starts from a position of trust and only uses captcha's when it is not certain you are a human, giving you a second chance to prove your comment is worthy.

I had a look at the statistics page of Mollom and noticed the weird notched pattern in the graph. Upon closer inspection it appears the "Ham" curve has a dip around every Sunday. I assume that is a result of people being less likely to spend their Sundays browsing sites and commenting; probably something to do with religion.

I think it is kinda funny to look at it from the other angle though... on Sundays comments are more likely to be spam.