The International Astronomical Union has been having an ongoing debate over the classification of Pluto. The more we learn about the solar system the less it makes sense to consider it a planet.
The problem is rooted in the fact that the criteria for what define something as a "planet" have never been explicitly stated. As tacit is fond of saying, fuzzy language leads to fuzzy thinking. Does an object have to have a minimum mass to be a planet? An atmosphere? A sufficiently spherical shape? Moons? These questions were never considered when Pluto was first discovered, and now that vagueness has created a disparity. It seems that in order to be consistent we either need to "downgrade" Pluto or accept a few hundred other bodies as being planets too.
Other objects have been discovered within our solar system which are of similar mass, yet they're classified as asteroids or cometary nuclei, so increasingly it seems that Pluto is a planet only because we call it one. This is precisely correct. The universe is under no obligation to fit within our arbitrary classification systems, and whether Pluto is defined as a planet, asteroid, planemo, planetesimo, cartoon dog, or god of the underworld has no effect on reality whatsoever- only our internal perception of it. Yet people, both astronomers and others, get surprisingly emotionally invested in what we call a chunk of rock that likely none of them will ever visit.
I think the reason for this is that we often forget that words are merely symbolic representations, and imprecise ones at that. We think symbolically, and this dependance upon symbols is the foundation of all of our complex relationships.
Here's an absurd example. Like every other interpersonal relationship, it could be argued that my relationship with femetal isn't so much with her as it is with my mental model of her, and vice versa. I know her well, which is to say that my mental model of her is similar to her actual self, and more importantly to her mental model of herself. If tonight she were to reveal to me that she's a Terminator (in the cyborg-from-the-future sense), my most enduring emotional reaction to this revelation (after the shock and sexual arousal had passed) would be a profound feeling that she was no longer the person I'd thought she was. Of course, from her perspective she wouldn't have changed at all- only my mental model of her would be different.
Changing gears just a bit, I've always been a bit squicked by the idea of destructive uploading. After all, even an exact copy of me is still just a copy, and the "real" me would be obliterated, right?
Now I'm not so sure. In fact, the more I think about it the more I realize that the entire question of "is a copy of you really you?" is likely just another result of fuzzy language. I suspect that the idea of "you" as an individual is flawed. "You" isn't an individual. "You" is a set- a group of parameters that seek to describe a dynamic entity. That set may only have one member right now, but I think that as the future unfolds around us this subtle distinction will become more important, and those who can't or won't wrap their brains around the difference will have a harder time dealing with the world.
Attempts to define an individual as a particular clump of matter or as a continuity of experience are as flawed as the feeling that Pluto's classification carries significance for the planet (or whatever) itself. Compare me now to me 15 years ago. Even though there are significant similarities, there are also unmistakable differences. Which one is "me"? Both. The differences in experiences and matter don't change the fact that "me" is nothing more than an symbolic representation.
So, if we could make an exact duplicate of you, would it be you? Does it start out as you, and become someone else once its experiences differ from the original you? Does the difference even carry meaning? As with a lot of transhumanist topics, equating people with software seems to give a much clearer perspective.
Gir is running Mac OS X v10.4.7. So is femetalscupcake. So is Gir's old chassis. Which one is the "real" implementation of OS X? They all are, even though they're vastly different from each other. Again identity defines a set, not an individual, even if only one individual fits within the set.
That said, if at all possible I'd still prefer nondestructive uploading, thank you very much. As much as the copy that lives on in The Machine is me, so too is the one that gets destroyed, and even with a backup I'm not a fan of being destroyed. :-)