As a 25+ year Youth Development Professional, this topic hits a nerve with me. I am reading more and more on these boards and in books like the one you mentioned, parents stating that their kids cannot wait patiently in line, therefore they resort to tactics similar to this one you are talking about.
Children are by nature fidgety. Waiting in line or waiting your turn is a learned behavior, not one that comes naturally. Parents are not doing their kids a favor by avoiding lines or waits. Kids learn by experiencing. Waiting in line is a learning experience.
But now you have parents going out of their way to ensure their kids are never discomforted in anyway. They feel the necessity to install a DVD player in their car so the kids are not bored during the ten minute drive to the grocery store.
I recently saw that a chain of grocery stores is test marketing carts that parents can rent that have a built in DVD and video game system to entertain the kids while mom is shopping.
If children never experience the discomfort of waiting in line or waiting their turn, they will never learn patience.
I can not think of a better place than Disney for children to experience the discomfort of waiting in a line and the reward for their patience. Parents should explain to their kids "If you want to ride Dumbo you will have to wait patiently in line." The child then knows what is expected and he/she is rewarded if they wait patiently. If the child becomes too fidgety, she/he should be corrected. If they continue the inappropriate behavior, the parent should remove them from the line and explain that the reason they can not ride is because they were not able to wait patiently.
In addition children to need to learn concepts such as "fairness". Is it fair that other people have to wait in line and they don't?
Sorry for the soap box, but like I said, this issue hits a nerve with me.