Sensation has a new theme every year. With the revelation of the theme of 2012, they wanted to have their Facebook-fans play an active role.
We decided to create a big board where fans can "tag" themselves and claim their own square. When claimed, that square would disappear and reveal the poster of the theme one by one. Ultimately we needed about 10,000 users to claim every square. As a further incentive, we hid 2 free tickets under several squares.
The system was developed in such a way that you could keep the tab open all day and watch the revealing take place. It was very cool to see fans swarming to the page and direct other users to reveal certain squares that they believed held information. Letting people share their claim on their wall further improved a viral feeling.