This sounds a lot like what Vidoop tried to do. Their initial idea was to replace passwords with an authentication mechanism based on selecting a number of pict

This sounds a lot like what Vidoop tried to do. Their initial idea was to replace passwords with an authentication mechanism based on selecting a number of pictures that fit into user-chosen categories. A person would select 3-5 images from a grid of 12 with each image belonging to a distinct category. Those who picked the images, in the correct order, corresponding to their chosen categories (selected on sign up to the service) along with their username was deemed authenticated. As far as I know they hoped to make money by selling ads within the categories, so if one of the categories displayed was "pets" you might see ads for petfood for example. They moved into doing captchas at some point too. Anyway, it seemed like a promising idea, but they folded last year. Good write up from a former employee here: http://factoryjoe.com/blog/2009/06/05/the-fall-of-vidoop/ http://factoryjoe.com/blog/2009/06/05/the-fall-of-vidoop/