Ross Floate sez: "When we build things for people, I always ask, 'How could someone screw this up for shits and giggles?' People tend to think I’m joking, but I’m deadly serious because if your site, network, or product becomes a playground for a bunch of jerks, it turns off the people whose time and attention you’re really trying to obtain."
When I've worked on transmedia experiences that have interactive/user-gen content touchpoints (such as Byzantium and Deja View), our creative teams have always asked Floate's question, and then built systems to proactively address the behavior of such curious users.
I want to characterize these users as mischievous imps or destructive trolls, but that's usually an unfair assessment. Whenever people are invited to participate in a thing that has a formalized system—a thing with rules—there's a subculture of folks who'll naturally want to stretch the boundaries of its design, if only to see how elastic (or static) those boundaries are.
These are the same people who command their Mario to run to the "left" side of the screen in a Super Mario Bros. game, to see if the screen scrolls in that direction—even though every environmental cue tells players to run "right."
Truthfully, I admire that kind of creative, unexpected thinking—and when I embrace that impish curiosity as a user/player on my own and test the boundaries of others' systems, I grin when I discover my curious behavior was anticipated by the designers.