Just curious, to stir the pot a little more.... does anyone know of, or seen, or actually heard, or even read anywhere where someone was riding in the back of a 5er or a TT and the trailer was involved in an accident? If so, what was the outcome of the passengers in the trailer? In the real world setting, has this actually happened? We can speculate and theorize till the cows come home. Real life examples might be more beneficial to this discussion.
If no one responds, then I can assume no one has actual first hand knowledge, so pretty much everything discussed here, about how dangerous it is to ride in a trailer is all speculation.
And FYI, those who posted that they don't let anyone ride in their campers, even to the point of having the "smarts" to get a 12 seater passenger van, you have most definitely chosen to do a wise thing. No one will every argue the point of riding in the tow vehicle... ever.