Good comparison, Mark. Then there is this thought experiment: Mark (possibly not you Mark, just a Mark) walks into the human copying machine and two Marks walk out. However, we cannot have two identical Marks in the world, so we must kill one of them. Does it matter which one we kill? The copying machine is perfect, so there is no way to tell which Mark is the original. So if it matters which one we kill, there is a 50% chance of getting it wrong. And it sure as hell matters to the original Mark, right? Or does it? Doesn't it matter just as much to the new Mark? Does either Mark have a better ethical claim on the life of Mark? (Oh, I forgot, by Star Trek rules, the new Mark has a beard and is evil. We'd better kill him.)