But CAPTACHAs have another purpose and are already making revenue as i blogged about in August 2008:
The Effort is to help digitalize print and is quite interesting use of the technology that many people just find annoying (i tend to enjoy the challenge!):
"Efforts to digitize (really) old books and newspapers were being hampered by faded ink that confounded OCR software. The solution Luis von Ahn came up with was to use the words that the software couldn’t recognize and insert them into these so-called reCAPTCHAs and use the power of human brains to decipher them. CAPTCHAs serve up two words, one is the security word, the other goes toward the book digitization effort."[Edited] - adding another CAPTCHA for good, a prototype from a reply to my post by @kentbrewster : Missing Kids CAPTCHA -- a Hack for Good
The New York Times is using this service to digitalize their archive that goes back to the 1800s (and paying for it). This ReCAPTCHA service as been a project at Carnegie Mellon where the CAPTCHA technology was born (but is being spun out as its own company) . The project is also doing work for free for the Internet Archive’s project to digitize every book published before 1980 which is pretty cool.
Aside from not wanting to see more advertising on websites i visit, i would also miss the inappropriate CAPTCHAs that pop-up every once in a while but perhaps they can be replaced with inappropriate advertising....