DARPA Red balloons at MIT

The DARPA network challenge has been won by the MIT team: MIT wins $40,000 prize in nationwide balloon-hunt contest

"On MIT's Web site, a link was posted inviting people to sign up to help find the balloons and urging them to invite their friends. It said the MIT Red Balloon Challenge Team "is interested in studying information flow in social networks, so if we win, we're giving all the money away to the people who help us find the balloons!"
It detailed a chain for giving away the money, beginning with $2,000 given to each person who first sent in the coordinates of each balloon.
"We're giving $2,000 per balloon to the first person to send us the correct coordinates, but that's not all -- we're also giving $1,000 to the person who invited them. Then we're giving $500 whoever invited the inviter, and $250 to whoever invited them, and so on..." it said."

Here are some of the details from the MIT site linked to above...
The Challenge
This Saturday, December 5th, DARPA will be deploying 10 large, red weather balloons at 10 fixed locations in the United States. (more info) DARPA is giving $40,000 to the first team of people to find all 10 balloons. Join the MIT team, invite your friends and you can win money, help science, and help charity! (see how it works) .