So in groups that hike separately and camp together, WHO if anyone is responsible if someone does not show up? That loose organization is fine as long as everything goes OK. It also works better with a few people, but gets more difficult to control with larger groups.

I really hate the anxiety that is produced not knowing if or when the person I am with is going to show up. If someone goes with me, I feel extremely responsible for them. I would rather slow my pace than worry all day about someone.

On our NOLS courses, search and rescue is actually a part of the curriculum, so having a lost person is actually a "teachable moment". Evacuating an injured hiker is also taught. I worked about a dozen 35-day courses for NOLS, and I recall only two evacuations. We always found the lost or they eventually show up on their own. The way a commercial outdoor school is set up is really quite different from loosely organized volunteer hiking groups. For one thing, a group of 20, with three professionals, has the manpower to actually do a search and rescue. Of course, that was in the days before GPS or any other communication technology.

For a smaller volunteer group, it is better to just send out for professional search and rescue.