As ever google has bought up another company. This come's from the well informed blog of John Battelle. Battelle says that Google has purchased the ESP game. He describes it thus:-
Google has licensed "The ESP Game", invented by Luis von Ahn, and is harnessing collective intelligence to tag images in its image database. This is just an experiment, of course. But it's a clever one - -if a critical mass of images are tagged, Google will have solved a very intractable problem for itself.
Anyway, I'd blogged previously about this before. The game is really cool. Give it a spin. Just don't tell those Google guy's we're tagging though.