The Georgia motorcycle drivers handbook advises "when riding in staggered formation, keep ONE second between you and the rider in front of you" ONE second is not enough.
I was recently involved in a 2 bike accident. Riding staggered on a 2 lane road, my "trusted" riding buddy and I ran into a severe rain/lightning storm. I spotted a safe place to pull over and gave hand and turn signals as well as flashing the brake lights. As I turned off the road he rear ended me at about 5 mph. We both went down (more like tipped over), minor damage to both bikes, but he broke his knee. Now I am being sued by him for negligance. No fault besides weather conditions were assigned by the police. Makes it difficult to want to ride with anyone behind me anymore.