I was always scared at the idea of riding close to others and took measures to prevent that from happening in group rides. Not that it actually mattered, I am a slow rider and was always riding by myself at group rides after 10-15 minutes anyway.

To be fair and honest, I am unsure if my problem was truly not trusting other riders, or my own ability/skill of dealing with emergency situations if something happened. I was far less concerned about dealing with rednecks on back country roads than I was riding around larger number of cyclists.