Greater love hath no man than this, that a man lay down his life for his friends. John 15:12
Of course, more of us would be likely to make sacrifices for people we know - our friends, family, neighbors and whatnot are important to us. The thing is though, we wouldn't necessarily be willing to make the same sacrifices for people we don't know at all - they wouldn't hold the same meaning to us. If you hear about 100 people dying in a plane crash, you'll basically shake your head and go 'that sucks, but oh well', but if just one close friend dies you'll be far more shaken up.