reCaptcha used for digitizing text
I never thought of Google's reCaptcha process as anything more than a way to catch spamming robots and prevent them from getting on forums and other Internet resources. Apparently, Google also uses reCaptcha to help digitize text for its various digital text offerings.
Lately people have spied what appear to be street numbers from homes and businesses being used as reCapcha images. Google has confirmed that it is testing the use of Street View images and using reCaptcha to digitize the text for Google Maps.