Friendly fire feels like complete bullshit, but it seems to always happen, and probably always will.
In the battle of Nasiriya my brother saw 4 of his battle buddies get mowed down my an Air Force A-10. 2 of which were in a vehicle with a blue force tracker.
So the pilot, who as far as i know is still not named, was told by the ground controller that there was no Marines in the area. This confuses me because not only was there an eye in the sky, but a 10 digit grid for air support, and BFT (blue force tracker)