Talking about tests before joining DP... I used to have maths captcha on one of my forums. The number of new registrations went down dramatically. I think i know why.
That would kinda decrease the amount of new members dramatically. I mean, people have a hard time doing 1+2+3x4. I suck badly at math, but i think it's absurd people joining this forum, calling themselves programmers, and fail to give a correct answer on such an easy math question.