We all do it. Why do we see the sacrifice that Jesus made as such a difficult choice? Why raise up as heroes those that die to save others? We are all going to die, it's just a question of when and how. Wouldn't you give your life to save your children? I know I would, without hesitation. And I would for any child I could save. With adults the decision becomes more difficult, at least for me: would you give up your life for a stranger? Someone you don't even like? It is still an easy choice when you talk about groups of people, again, at least for me.
Wouldn't 90+%(?) of people sacrifice themselves to save all of mankind? I think a much harder moral question is one raised in the movie Swordfish; who would or could you kill in order to save another person/group of people? Would you kill 1 to save 1000? Kill one to save 100? 10? You can make this arbitrarily difficult, but the ultimate question is the same: if you kill some to save many is that more moral than allowing the many to die, but not by your hand, and what if you can't guarantee that if you didn't kill the one, then the X would die?