Just that we try to make sure that what happens inside games stays there. There are Judges who love trying to turn us against each other, or making us hurt each other; if we let that spill over outside games, things tend to get unpleasant.
There are twenty-eight Judges that we know of, plus three destroyed or inactive. In no particular order: King, Queen, Messenger, Beauty, Persona, Storyteller, Mirror, Game Master, Beast, Flowers, Haunted, Veiled, Angel, Clockmaker, Foreman, Gambler, Lover, Shadow, Soldier, Dude, Kid, Twins, Graces, Waterbearer, Huntress, Horn, Guardian and Librarian. Of those, the ones known to regularly be dangerous are Huntress, Game Master, Flowers, Storyteller, Persona, Mirror, and Horn in combination with certain others. The rest may or may not be, but tend towards harmless. Guardian watches over the Judges' enforcers, Ophiuchus; he doesn't run games. Waterbearer may or may not still be alive and sane, at this point; we don't know.