Protecting Website Registration. ( E-mail services: Yahoo, Microsoft, Google )
Preventing Dictionary Attacks (in password systems). Prevent a computer to iterate through the entire space of passwords by requiring it to solve a CAPTCHA after a certain number of unsuccessful logins.
Search Engine Bots. It is sometimes desirable to keep webpages unindexed to prevent others from finding them easily.
If the world's computer Solitaire players could be coaxed into enjoying a game that contributed to solving a computing problem, he calculates, it would produce billions of man-hours of labor each year.
„ make all of humanity more efficient by exploiting the human cycles that get wasted“