Just to make sure this is clear to everyone: it is not a test for humanness. I haven't found a CAPTCHA yet that tests if someone is a human. And, humans send spam.
I won't do any monkey dances (captchas) for any sites that are not absolutely necessary, like getting access to government services or public transport. I've skipped joining a few forums that looked interesting because they had CAPTCHAs, which is a group of letters that translates to
"We have a spam problem, and we require our users to fix it for us, because they are lowly users and we would rather make them do a monkey dance than we actually do all the well-known techniques we ourselves are responsible for doing instead."
I did look at the page, but couldn't figure out what exactly I was supposed to do. I'm probably too stupid for such a thing, which prolly means this works perfectly: you wouldn't want stupid people like me commenting on your whatever website.