It seems that the key here is to learn and understand your limitations. Not only your marksmanship limitations, but also your ability to determine range, and at very long range to calculate range with a very small margin of error. There are also an infinate number of variables that effect the bullet's flight as the range lengthens, and each must be calculated into the firing solution for the shot to be successful.
When we talk of taking big game at ranges that approach or exceed half a mile, we are looking at some very specialized equipment, and very specialized marksmanship ability. The more that stories circulate about that type of shooting the more likely the uninitiated are to assume they can do it too; that there might be more too it than adjusting your scope to hit 30" high at 100 has not occurred to them. After all, if I can shoot 1" groups at 100 then I can shoot 10" groups at 1000, right? Those of us who have shot paper at 1000 know it ain't necessarily so, but you have to do it to know that.
It takes a very good marksman to get a 300 yard kill shot on a live target, yet there are some who seem to suggest that there is nothing special about a 300 yard shot. It depends on the circumstances, but sometimes a shot should be passed up regardless of range. The temptation though is to take the shot regardless of range.
A few weeks back I was out on the sea ice and was able to put the sneak on a seal and get within what should have been easy shooting range, which I estimated at 150 yards. My rifle was sighted for 150 yards so all I had to do was hold dead on and press the trigger, right? Well, not so fast. The seal was broadside to me, when they are head on or straight away, there is a greater margin of error, because when broadside, unless he lifts himself up to look around there isn't much to shoot at. My position was solid, I was slung up, and I could have not have had a better hold from a bench rest; but I was in the pressure ice about 5' or 6' above the seal. Now, where is the bullet going to go? My horizontal wire completely covered the line of the seal's body. The seal was still and wasn't lifting his head so I had very little margin for vertical error. I put the cross hair dead on center, while my brain screamed, "Aim low!" But a few feet of elevation of the firing point can't make that much difference can it, and if I am slightly high and hit the spine so much the better. So I aimed dead on, pressed the trigger and the rifle boomed . . . the seal disappeared down the hole. This will happen sometimes if you don't get a CNS shot on a seal so I wanted to look for signs of a hit. I walked over to the hole and there was no hair or blood to be seen. Keeping an eye on my firing position and the hole I walked away from the hole and 30' away found my bullet strike in the ice. That bullet couldn't have been more than an inch over the seal, but a miss is just that - a miss.
Now most folks will concede that a 150 yard shot on a live target is within the ability of any competent marksman. Certainly that shot would have dumped any big game animal under similar circumstances, but if a competent marksman can make a mistake at 150 yards, does he have any business shooting at a big game animal beyond 300? For me 300 yards is far enough, and I have no problem passing up a 300 yard shot at unwounded game, but that is for me and it is not up to me to pass limitations on others. I only hope that those who make a conscious decision to shoot at a big game animal at long range do so with a full understanding of the problem, and that they do so recognizing what is an opportunity that offers a high probability for success but also recognize what circumstances offer a high probability for failure.