I will accept the fact that the general consensus here is that it shouldn't be done. But I must say, the logic is flawed. The point that everyone seems to be making is: "how would you feel if 10 additional people all of a sudden jumped in front of you and put you further behind in the line?" Well...you would be in EXACTLY the same place if those 10 people had been in front of you all along. You are not negatively impacted by their presence, irrespective of whether they appear one minute before you join the line or whether they appear one minute before the line starts to move.
Let's look at an example. You choose to see two consecutive performances of F!. At the first performance, you arrive two hours before the show and get in line. A group of 10 people arrived 5 seconds before you and are immediately in front of you, and they are the first ones in line. You are the 11th person in line. For the second performance you arrive two hours before the show and get in line. A group of 10 people arrived 5 seconds before you but they leave only one "scout" to hold their place and he is immediately in front of you. He is the first person in line. Had the entire group stayed, you would be 11th. But because 9 of them left, it appears that you are now second. However, 15 minutes before the line begins to move, the other 9 reappear and you are now 11th in line, same as you would have been had the other people stayed. Your place in line hasn't changed. Only your perception of it.
Now, for those of you who say: "Yeah, but those 9 people got to have fun while I didn't." That argument only works if you are traveling solo, which most people do not do. Everyone has an equal opportunity to engage in the same behavior. If it were "generally acceptable behavior" and everyone did it, no one would mind. It is only the people who think that this is wrong and refuse to participate who do not benefit. The better solution is for everyone to have a "gentleman's agreement" that standing in lines for hours at a time is an inefficient use of time and that place holding is acceptable. Once everyone came to that consensus, we would all come to realize that place holding is actually far preferable to line waiting, especially when children are involved.
We do this every day. When we go to the movies, one person waits in line and buys all the tickets. Otherwise, the lines would wind themselves out the door of the theater. While one person waits in line for tickets, another person goes to the concession stand and buys all the food. No one has ever complained about this system. In many situations, the entity in charge of the line will hand out placeholder numbers or wristbands and tell everyone to come back at a specific time, lining up in accordance with their number. This would work just fine with F!. People could appear any time up to 2 hours before the show and get a number. Then, 30 minutes before the show, everyone would reappear and line up in order. "What number are you? 57? Oh. OK. I'm 62, so I must be just a little bit behind you." My guess is that no one here would complain about such a situation. But the "scout" placeholder system is EXACTLY the same thing, only it is self-implemented and not "sanctioned by the park" and as a result, people seem to think it is wrong.
I would suggest that we use the power of this board to shift the way we all think. If we ALL could reach the consesus that placeholding is more efficient and more enjoyable, and everyone did it, then no one would feel offended or cheated when it happended.