That works on a small scale. But, when your site gets enough visitors, it is worth it to a spammer to spend five, or ten, or fifteen, minutes figuring out all o

That works on a small scale. But, when your site gets enough visitors, it is worth it to a spammer to spend five, or ten, or fifteen, minutes figuring out all of your questions. So, it's a potentially useful trick for sites only targeted by very dumb bots. But, the bigger your site, the less likely it is to work. My sites aren't even that big (anywhere from 40k to 250k visits per month), and this technique isn't tenable for most of them. I do use it on our wiki (mostly as an experiment, since CAPTCHA isn't as accessible as I'd like), which is the 40k visits/month site, and it needs new questions every couple of weeks, or we get hammered. And, all of our sites have other mechanisms for preventing spam, as well.