CAPTCHA farming:

CAPTCHA-cracking ... is a booming sector of the Indian tech economy. [ZDNet writer Dancho] Danchev reports that CAPTCHA-crackers can earn more per day than they can as legitimate data processing centers.

Indian CAPTCHA-crackers (perhaps they were Chinese gold farmers in another life) appear to earn between 1/10 and 1/8 of a cent per CAPTCHA solved. The businesses in question advertise a wide range of available CAPTCHAs per day; smaller outfits claim they can provide 25,000-50,000 solutions per day, while large-scale operations advertise themselves as producing up to 700,000 CAPTCHAs in a single day.

Here's the ZDNet story, "Inside India's CAPTCHA solving economy".