I think since more and more ACCF players try to play with codes (reasons for restoring grasses, watering flowers, etc), so by that trend, there will be more potential or probability for having such a situation (access to codes that work on-line and could be used to harm other players).

Just watch-out when inviting other players to your town or when visiting other towns. Like Nintendo says, only exchange your friend code to people that you can trust. Or use *magic* so you could reduce the severity of problems when they happen (like your town gets destroyed, etc).