Just encountered this on a group hike-and-camp last weekend; the group size was about 12. It was an overnighter, organized by the local backpacking shop (we have a great outfitter, and they do a nice job with these trips.) There was no connection among group members, except that we're all shop customers or staff (there were a couple of husband/wife teams.) Mostly, we didn't know each other well.

On the way in, we pretty much all hiked together (or in 3 or 4 loosely connected groups), and all waited periodically to get everyone together - typically at a trail junction, or somewhere that the trail became a bit hard to follow.

The next morning, we had the typical situation where two of us woke up early (6am), had our packs halfway packed before we left the tent, and finished packing a couple minutes later; we then ate a cold breakfast, and were ready to go by 7:45 - which was about the time everyone else was emerging from their tents, to stumble over to the fire ring and stand around trying to warm up while waiting for someone to ask if it was time for breakfast yet. At the rate they were going, it would be at least 9am until any were ready to leave.

There was no pre-agreed protocol, and neither of us were group leaders. So, the two of us decided to go ahead and start hiking, bid everyone a friendly farewell (they did all turn out to be nice folks), and hit the trail. We had a great early morning hike out, and got to know each other a lot better and found out our hiking and camping styles mesh nicely (in fact, I think I may have found the hiking partner I've been missing the last few years; we've already got another hike planned.)

So, I'm just interested in what the rest of you do in those "social" hiking situations, and what the etiquette might be: would you have set off yourself, or waited until everyone was ready?