It's the most basic interaction in the game. Two players meet in the wastes, someone yells "I'M FRIENDLY I'M FRIENDLY", and then eventually everyone dies.
While playing DayZ, TheRunningManZ ran into an underequipped stranger. Everything was pretty standard until they got attacked by someone else, who was actually the stranger's friend.
What made it so interesting is how they did it. They pulled a great bait-and-switch, where the friend fired a few shots, killing one of the group. He the drops the gun (the only one they had) and runs away, attracting everyone's attention. Then the first stranger can pick up the gun and continue attacking while everyone's distracted.
This all apparently got RunningManZ thinking, and he comes to the conclusion that telling someone you're friendly when you're unarmed is basically equivalent to saying "please don't shoot me". It only really carries any weight when you're saying it from behind a rifle.
So DayZ newspawns, try and think of something new to yell. At the very least, it'll add some variety to the DayZ videos out there.