Google's CAPTCHA experiment and the human factor

Captchas were designed to distinguish bots from humans. But that's no longer the problem[1].

You've just got to assume even a "bot" is human now. Casinos don't spot many cheaters at the door, but rather spot them in the act by monitoring their behavior.

[1] Though still an issue, I don't think removing them totally would do much good, you still dont want people cause semi-malicious damage of your site for even non-profit reasons, such as the Time 100 poll which has been gamed by 4Chan (not that Time introducing a captcha has stopped them though, just slowed them down — however I highly doubt they'd have started it if the captcha was in place from day one)

I wish more people would realized how cheap and easy it is for spammers to break captchas and how extremely hostile captchas are towards people with disabilites. Deaf-blind people aren't helped by the sound alternative, the few times that's even an alternative. The only protection captchas give is one of inconveniance for spammers, it's not a working obstacle and the whole idea is flawed.

Spammers can be fought by traffic analysis, communication caps and community based moderation. Even if you are absolutely insisting on captchas please don't do it as a first line of defense, use them on spikes like how youtube handles mass comment voting.