We have a similar dilemma regarding aircraft booking. In every system, there is a risk that the a/c won't return in time for some reason, and the next guy will have his plans ruined and will heavily protest. Who is going to be punished? (The answer: the guy who flies less and makes less profit for the operators, i.e., doesn't depend on being 1st or 2nd.)
One of the reasons I left the club I was flying with and bought a share in my own plane was because of exactly that type of thing.
I had a plane booked for a whole day because I was taking my wife to France. The evening before my flight I popped into the club to prepare the paper work to make the morning a lot smoother. By that time of the day all the next day's bookings had been added to the wall.
I notice that my day had been hijacked by another member who had got one of the staff to erase my booking so that he could have the plane. I now only had a 2 hour slot from 10.00-12.00.
Obviously I asked what had happened, but the guy in the office was on the phone. When he got off the phone I asked again. He told me I was in luck because he had just put the phone down from the guy who had booked my slot, and he couldn't make it, so I could have the plane the whole day after all.
I pointed out that a) just because this guy had been a member longer doesn't give you the right to amend my booking in his favour, b) no-one had even had the courtesy to call me and discuss, and c) he was the one in luck because he wouldn't have been flying that day because I was still going to France, and wouldn't have been back until sometime in the afternoon.
It wasn't long after that episode that I left the club.