Wow, that was fast. Anyone have any info on how they did it?

EDIT: From http://balloon.mit.edu, it looks like they just created a system to assign personalized tracking links to which you could submit pics and coordinates of balloons, as well as invite other people to get a personalized tracking link of their own. If you found a balloon, you got $2000, plus your inviter got $1000, plus their inviter got $500, etc, etc. Simple but obviously effective.