Humans are the problem, not some mythical AI powering the bots. It costs a fraction of a cent to get a CAPTCHA solved. The only real counter being used is making it take longer to solve a CAPTCHA - which is exactly what the services like reCAPTCHA do, while minimizing the impact on heuristically 'good' users.
Making CAPTCHA solves take 30 seconds or a minute instead of 5 seconds is the state of the art.
The heuristic google uses for 'good' is 'compliance with the google surveillance system.'
And if throttling attempts is in fact the state of the art as you claim, you can do that without pulling in google code at all. I trust you are that competent at least. However the fact that the noscript version doesn't make you wait at all leads me to conclude your excuse for google's behavior is bullshit.
Making CAPTCHA solves take 30 seconds or a minute instead of 5 seconds is the state of the art.