Google uses reCaptcha to recognize street names and house numbers.

Recently, many users began to notice reCaptcha with pieces of photos containing house numbers, street names and even road signs.



A Google spokesperson confirmed that they are experimenting with people to improve the quality of their database of information on addresses and businesses using Street View photo recognition.
Based on the results of these inhuman experiments, a decision will be made on the use of reCaptcha for other tasks.

A small collection of such caps, collected by the user of the blackhatworld.com forum:
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(clickable)