Have you ever struggled to read a CAPTCHA?
IF (false) THEN
Did you know Google has been crowdsourcing corrections to its digitised books for a couple of years now by using their reCAPTCHA service – see http://www.google.com/recaptcha/learnmore. So those sometimes hard to read words were actually often taken from texts and they were too hard for a computer to read, so they were outsourced to you.
Over 5 billion corrections have been made not by volunteers but by websites making millions of people fill in those 2 word CAPTCHAs that verify that you are not a spammer.