If you've ever signed up for a forum account or newsletter on the Internet, you have probably run across the ReCAPTCHA system that has you enter characters you see in an image on the screen to prove you're a real person and not a spammer robot. For some reason, I always have a hard time making out letters in most of the ReCAPTCHA images.
Google is now using numbers from home addresses and street signs as part of the ReCAPTCHA system. Google has confirmed that it's using the little images from its Street View image collection in its spam fighting system. The goal is to improve Google Maps by letting the users identify street names and business addresses.
The reason this seems so strange at first glance is that many of us may not realize that other than helping reduce spam, ReCAPTCHA also helps to digitize text and printed materials for Google Books, and Google News archives. This is a very slick way to kill two birds with one stone on Google's part. The images don't appear to show the home in any identifiable way, rather the photos simply show the house number.