The whole point of this system is that you do not ride as a tight group. Indeed you are encouraged to ride at your own pace and you could be out of sight of the preceding and following riders. If everyone does their job properly every time you come to a turning point there will be a rider parked in a safe place indicating the direction.
If you spread out, maybe a couple of hundred yards between riders,you do not impede other road users and do not cause any frustration to following traffic. It is also safer as you are riding to the conditions you see ahead of you and not blindly following another rider.
You can end up marking a turning point for quite a while, possibly 10 minutes, if it is a large group but you can spend that time stretching your legs or otherwise relaxing until the back marker arrives
As has been said it does rely on everyone on the ride understanding and following the system. If a rider has such an ego that he is not willing to abide by these quite simple rules do you want him on the ride with you anyway?
"Pace
Followers shouldn't ride faster than they're completely comfortable with. There is no need to keep
up with the rider in front. Ride at your own pace. The ride will adjust to the slowest rider, without
slowing down those who wish to ride more quickly. The slack is taken up by the time spent Marking.
Spread out. If you ride with small gaps between successive riders then there is a tendency to just
follow the rider in front rather than planning and executing your own ride. Your view ahead will also
be obscured and overtaking will be trickier. You'll get more out of the riding if you open up a
sizeable gap.
Overtaking
Overtaking is permitted and indeed encouraged within the group. Faster riders in a slow group may
do a lot of overtaking, which also means that they get to mark junctions more often and help maintain
the pace of the group as a whole.
Take care when overtaking, and ALWAYS USE SIGNALS to overtake. Do not obstruct or tailgate
other riders. No 'cheap' overtakes. Do not overtake the Leader."
Can the system fail? Of course it can, often when a marker gets fed up waiting and just disappears, but sometimes an accident or breakdown occurs, but with the Leader and Backmarker able to contact one another it does not take too long to get everyone back together again
"Breakdown or Accident
Whether or not other riders have already stopped, the Back Marker will come upon the incident in a
matter of minutes, and will communicate news of the incident to the Leader using both mobile voice
and SMS text messaging.
Having received the news, the Leader may choose to return to the site of the incident or to remain
where he is, depending on the circumstances. If he decides to return he must retrace his route picking
up Markers on the way.
If the Leader does not receive the news he will eventually run out of Markers and stop, or reach a
scheduled stopping point."