depends on the mod, right?.  Some might want to change site defaults; others might want to be more specific.

In general, I think we want to steer people towards good decisions, but we don't really want to presume to make bad ones impossible.  This is why freeze bugs me; it's so hard to override.  In other cases ruby has nice tricks for overriding when you really need to, like :instance_variable_set, for example.