Design, don't constrain
People don’t like to be configured. They don’t like to be forcibly told how they should use a service. They don’t want to be told to behave like the designers intended them to be. Heavy-handed policies don’t make for good behavior; they make for pissed off users.
This doesn’t mean that you can’t or shouldn’t design to encourage certain behaviors. Of course you should. The whole point of design is to help create an environment where people engage in the most fruitful and healthy way possible. But designing a system to encourage the growth of healthy social norms is fundamentally different than coming in and forcefully telling people how they must behave. No one likes being spanked, especially not a crowd of opinionated adults.
