Web Security Words Help Digitize Old Books: Dusie gave me a head's up about this story. If you missed it on NPR, go give it a look.
I found it interesting because back around 1992-1993 I was part of Princeton's digitization of its catalog, which digitized the actual cards. This was one of the first digitization projects (and you can see the results here), and they were doing it on a tight schedule and budget. They pulled all the summer workers from Firestone Libraries that summer for 2 hours of quality control a day, and we hated the tedium, and there were a fair amount of quality control issues due to the age of the cards, handwritten notations, the fading of ink.