Crowdsourcing, which exploits the collective intelligence of thousands of people to tackle big problems, has become popular in business, political, and academic circles. But Mark Harris described how a hacker and a friend infiltrated a DARPA-sponsored "Shredder Challenge" and created havoc. Participants in the challenge had to piece together 6,000 chads from documents that had been put through high-end shredding machines. Some of the teams used sophisticated computer algorithms to help match images of the chads that had been posted online. But the hackers managed to scatter pieces that had been matched, pile chads on top of each other, demoralize users, and drive hundreds of participants away. The researchers concluded that the hacking raised doubts about using "crowdsourced problem solving for sensitive tasks involving financial markets and national security." Science writer Paul Raeburn said Harris produced "a gripping, solidly reported account" that undercut blind faith in the wisdom of the crowd. Intrigued by a scientist's online comment regarding the DARPA Challenge, Harris started digging deeper into the program. "The more I explored it," he said, "the more this pacey tale of high-tech hackers turned into a critique of crowdsourcing itself."