I really enjoy Josh Hallet's Hyku blog. He writes about many things that interest me so I find myself leaving more than a few comments on his site. I really love that his spam filter requires me to answer the same question: the sum of 4 + 4. (Okay, I used a calculator to be sure, but now it's memorized.) If this lets Josh filter out the automated spammers, why does Typepad require me to match six letters and numbers that are often hard to read because of the lines going through it? I really hate having to pass spam tests on my own site as well as others.
I just think the simplest solution is almost always the best.