Maybe Julie Barker from Meetings Industry Megasite explains it best:
Meetings Industry Megasite
Entertain with Chocolate by Julie Barker
On the West Coast, Janet Rudolph runs a Berkeley, CA, company called TeamBuilding Unlimited that features a "chocolate challenge." She divides the group into teams of four or five people, furnishes chocolate-covered graham crackers, M&Ms, chocolate Gummy Bears, Hershey bars—"anything you can think of that is made of chocolate. We go for different shapes, sizes, and textures, not high-end chocolate."
Groups then compete to build a structure. One HMO firm had its teams build their ideal hospitals. Another group set its teams to designing resorts. The result "has to stand up on its own and, except for the white cardboard base, has to be completely edible," says Rudolph. Teams are given about an hour to design and build, and then they have to present the results. "Half the fun is explaining why they did what they did," she says.