Player villages are protected by claims that set these areas apart from the rest of the world, and these claims can be expanded by building certain structures. Griefers who set out to do harm or mischief against villages within these claims will leave a "scent" behind that can be used to track them. There are certain skills, such as ranging and tracking, that players need to have to follow the scent to the perpetrator, however. This opens the door for players to specialize in becoming bounty hunters who protect the village by rooting out enemies.
As for punishment, well, Creative Director Björn Johannessen expects players will take justice into their own hands -- and more than one perpetrator will pay the ultimate price for violating a peaceful sanctuary.
You can watch the full discussion of Salem's crime and punishment system after the jump.