Bob and Ken state the obvious. However, the obvious is not obvious to a lot of people. I see it every weekend in the winter to some degree in the SoCal mountains.
It has gotten to the point where, just say one thought provoking thing to these people and keep on moving, not looking back. The problem is nothing ill happens to these people, which reinforces bad habits and then these people are looked upon as experts by their friends.
My guess is 99 times out of 100 nothing will happen to the ill-equipped and unprepared on the MR but that one time is going to be really bad.