Well the whole "it's what ninjas do" concept is fine and dandy in a real ninja world where they have tools and methods to dispose of spies. However in our reality, an internet based game with no countermeasures, it is a bit of a spoil sport thing to do. It ruins the game on so many levels because it not only punishes those who were spied on but creates an issue where any new member attempting to enter a group then becomes scrutinized, carefully watched and, at extremes, exiled before even given a chance. I think something like this would be a great idea because it does stop a lot of this immediate behaviour.