That's great, pretty much any home-rolled CAPTCHA will perform great, simply because it's not worthwhile for spammers to design an attack. If that, however, was

That's great, pretty much any home-rolled CAPTCHA will perform great, simply because it's not worthwhile for spammers to design an attack. If that, however, was the default anti-spam mechanism on, say, wordpress installs, it'd be automated against in minutes.