Just to respond to some of the comments I've seen. Basically, yes it's true that my sites aren't very high profile, and if someone were to target them directly

Just to respond to some of the comments I've seen. Basically, yes it's true that my sites aren't very high profile, and if someone were to target them directly it would be trivial to bypass this system. The point was more that the current, well used bots that send spam randomly, do not work against them. Interestingly enough one of you, someone who saw the story here, decided to actually write one such bot and start spamming my blog post, but again they were pretty stupid and it was trivial to block. Still, pretty sad that someone would go to this length and actually try and send hundreds of spam posts just for the kick of it. Also a lot of people mentioned captcha, and yes I guess I should have mentioned that, but the reason I never used one is because I didn't get any spam in the first place.