1. ReCAPTCHA does a lot more than Project Euler's captchas... or to put it another way, the "Zero day" you're talking about would be worthless vs ReCAPTCHA: http://en.wikipedia.org/wiki/ReCAPTCHA#Security
2. Google requires a verified cell phone number for most of their services at this point, with the captha basically being a way to avoid spamming text messages
"Given that people still drive cars in 2014, I think we can safely conclude that the 1908 Ford Model T is still state-of-the art"
2. Google requires a verified cell phone number for most of their services at this point, with the captha basically being a way to avoid spamming text messages
"Given that people still drive cars in 2014, I think we can safely conclude that the 1908 Ford Model T is still state-of-the art"