I think a good chunk of the images are captured by way of Google's Streetview vehicles [1]. I'm seeing blurry images of house and apartment numbers all the time

I think a good chunk of the images are captured by way of Google's Streetview vehicles [1]. I'm seeing blurry images of house and apartment numbers all the time. So I'd imagine there are always new images popping up that Google can feed into the recaptcha system that haven't been seen before. [1] http://www.google.com/recaptcha/intro/#creation-of-value http://www.google.com/recaptcha/intro/#creation-of-value