I guess the part that I don't get is that, with today's cell phones, there is no logical reason to abandon anybody... Maybe the group should not be expected to turn around and go back -- but at least know what the situation is and, if it is not an emergency, they could send a car around after the ride is over (If it is needed).

But, if they are OK with simply leaving somebody stranded on the side of the road with a mechancial failure or even an injury to fend for themselves... well... That's not the kind of group I would care to ride with.