Google Image Labeler
vandalman writes to tell us that Google is betting on the obsessive compulsive need for many users to see big numbers next to their name with a new beta service called Google Image Labeler. From the description: "You'll be randomly paired with a partner who's online and using the feature. Over a 90-second period, you and your partner will be shown the same set of images and asked to provide as many labels as possible to describe each image you see. When your label matches your partner's label, you'll earn some points and move on to the next image until time runs out. After time expires, you can explore the images you've seen and the websites where those images were found. And we'll show you the points you've earned throughout the session."
I'm pretty sure I've seen some university project identical to this some time (1 year ?) ago. So it's definitely been done before. Although google does make a perfect (or at least a lot more suited) maintainer for such a project.
It's basically a licensed version of the work by Luis von Ahn, a grad student (and now professor) at Carnegie Mellon. It's pretty similar to his Peekaboom game.