You've used a self-service petrol station and put your own petrol in your car, you may have even used a self-scan checkout in a grocery supermarket or DIY store, but did you realise that whenever you type those random characters into a website that get generated to "prove that you are a human not a machine" you are most likely participating in Google's mission to digitise the world's books?
HBR article revealing some of the other clever and innovative initiatives to harvest the effort of unsuspecting workers.
