DRIDDLES and all - As a cyclist, and this will sound very hollow, I apologize to you for their actions. "Proper" etiquette is that they should be in a line of pairs of cyclists. When there is a vehicle coming from behind they should merge themselves into a single line. And if the group is that large, they should break that group into a couple of smaller ones so that they don't create a long line for motorists to pass around.
My only request is that when you do come up to other cyclists that are using good common sense that you give us enough room and time when you pass. I've had a number of close calls where just waiting 15 seconds would provide me, you, and oncoming car(s) enough room to pass without putting anyone at risk.