Good post, Jay. I've never thought these "Who are you going to save" examples do much to justify embryonic stem cell research (ESCR). The most famous is the "burning research lab" oft mentioned by Ellen Goodman and others. It goes like this: If you are in a burning research lab and you have time to save either an infant or a container of frozen embryos, which are you going to save? Since most people, even pro-lifers, opt for the newborn, we're told that's prima facie evidence that even we don't believe human embryos count for much.
The illustration is wrongheaded from the start. As Ramesh Ponnuru points out, ESCR is not a question of who to save, but who we can selectively kill. If I'm in a burning building and I have a choice between saving my daughter or ten other people, I'm going to leave the ten behind. But I wouldn't slit their throats on the way out, even if it increased my chances of survival.
The force behind these examples (whether they be burning research labs or flooded fertility clinics) is more intuitive than rational. Sure, intuitions are important indicators of right and wrong, but they are not infallible. At the end of the day, intuitions must give way to superior facts and arguments.
And those facts say that from the earliest stages of development, the human embryo is one of us--regardless of how I feel or behave.