I wonder if one couldn't use the large tagged database of images from the ESP Game for this: http://en.wikipedia.org/wiki/ESP_Game http://en.wikipedia.org/wiki

I wonder if one couldn't use the large tagged database of images from the ESP Game for this: http://en.wikipedia.org/wiki/ESP_Game http://en.wikipedia.org/wiki/ESP_Game To get a database that large, the spammers would have to set up their own ESP Game and tag a big chunk of the web. Even better, show two images, one with known tags and one unknown, so that you can build the database further, like RECAPTCHA does.