One thing to keep in mind, and this is probably not too much of an issue in here, but I've been on hikes with a group and one of the group is a much stronger hiker. They tend to want to push the pace and if the weaker ones try to keep up, it can cause someone to go past their own personal safe limits and get hurt.
Excellent point. For instance, here in the middle of Phoenix is a small mountain (Camelback). There is a 'trail' to the top, with the entire trip being 1.2 miles with about 1200-1400ft of elevation change that is a popular workout. Phoenix Fire Dept gets called several times a year to do rescues on this trail. I talked with one of the squad leaders and he mentioned that a large demographic for people needing rescue was guy hiking with a girl with the girl being the more fit of the two. They would just be doing their normal pace and the guy would be too proud to ask them to slow down and collapse. Women tend to be much more sensible about that sort of thing I have found.