I wish I were able to make this post witty but I can't. This is just how it is, so I'll try to keep it short.
Group rides are supposed to be fast. Especially flat ones. If the ride gets slow, people bunch up, and weak inexperienced morons start riding too close to each other. This leads to unnecessary contact, some hairy moments, and possibly crashes.
If the pace stays high, then the weaklings are just hanging on for dear life in a single file line behind you. It's much harder to lock handlebars with someone if there is nobody riding next to you.
I've crashed on the bike twice, and both times were because some moron though it would be a good idea to move up through the field by sprinting on that crack on the side of the road between the asphalt and the curb. Granted that the people tho do this are just morons, but if the pace were faster and we were strung out, then they would either be to weak to move up, or atleast they would have some space on the road to try to sprint around us.
In a race, there's a lot of other stuff to worry about, but in a group ride; Keep it fast. If others don't want to keep it fast, then attack. If they catch you, and slow down, attack again. It's really the safest way to ride a bike in a group.
That is all, maybe I can think of something more entertaining later.