@Amperage,
"I'd have to not choose thereby letting 9 people die who didn't have to...."
As someone already mentioned, "not choosing" is actually a choice you are making. The moment you become aware of the fact that you are capable of flipping that switch, your actions become your expression of your ethics.
Whether it is more important to save one or ten, however, is inconsequential. All people have different relationships to everyone else, therefore no one person is more important than anyone else.
For a person who is Catholic, he may opt to save the pope over two teenagers. For the secular father of those two teenagers, the pope is a goner.
For this reason, utilitarianism can not be applied to important ethical scenarios.
Utilitarianism is perfect for, let's say, deciding what toppings to put on a pizza. 5 People want pepperoni, 2 want sausage; pepperoni it is!
But when it comes to determining the value of human life, utilitarianism would allow for different people to place different values on the same subjects, creating a system of selfish chaos, much like the world of politics we live in today.
Instead, it would be more prudent to simply hop on to the tracks and untie those people before the train hit them. If the train is too close, then it seems like the situation would be out of your control.
This is the problem with hypothetical ethical scenarios, or thought experiments. They allow no room for choice, which is the basis of all ethics.