Earlier today when setting up a new Google Group for planning a CRAMBA event I noticed that Google’s reCAPTCHA service has moved from using just scanned book images (info on how this worked) to using house numbers which I suspect are from Google Street View. I imagine that this works well for them because house numbers are inherently human readable and successfully translating them to integers is likely key to their reverse geocoding efforts.
EDIT: Apparently this is old news. Shows how often I use reCAPTCHA… I first noticed it today.