somethingawful.com does something like this every week or so.

The newest one i heard about was of a race of aliens that plotted to take over Earth, but realized that they were like insects in comparison to people, so they took over the mind of a Microsoft employee to gain access to the Internet to destroy it and disrupt communications. The job of all the other forum members was to issue commands to the employee drone to accomplish this task (all while from the perspective of aliens that don't know anything about humans).