Some time ago I attended a talk by Ken Hayworth of the Brain Preservation Foundation, who discussed technologies for whole-brain scanning, and claimed that whole-brain emulation is the cure for death. I had a strong gut reaction that this is wrong, and asked everyone in the room the following question: if you were somehow copied and were told that either you or your copy must be destroyed, would you truly have no preference whether it is you or your copy that keeps living? I was surprised when everyone claimed that they would have no preference whatsoever, except two people. One of them (thank you, Kent) was as shocked as I was and shouted, "You're all zombies!"
My feeling was that anyone with a subjective experience would agree that what really matters is preserving this subjective experience, rather than preserving some information-processing mechanism that generates similar outputs to you in response to similar inputs. How can you think that a good world is one in which your ideas get expressed, your thinking gets thought, but not by you? The striking disagreement between this feeling and the people in the room forced me to reconsider this strong intuition.
I finally found a solution in the following thought experiment: consider a device which allows two separate brains to communicate as if they were two parts of the same brain. This is not ridiculously implausible: we can already "read" and "write" from/to individual neurons, we just need to do this on a massive scale and combine this with a low-latency, high-bandwidth wireless communication device, and add in some synaptic plasticity capabilities (allowing the same kind of modifications to happen between the two brains as within each one). Sure, we don't have that yet, but it's reasonable that we'll have that in the not-too-distant future.
Now, go ahead and connect your brain to your copy's brain. What is going to happen to your subjective experience? Given sufficient learning and if the plasticity is implemented correctly, I would guess that you would start experiencing the world somehow from both bodies. It's only a guess, but it seems quite likely to me. And once that happens… does it matter which one gets wiped out, you or the copy? Is there a clear distinction anymore?
This thought experiment helped me realize why it may not matter, although not on a completely intuitive level. I still don't see why it matters to preserve one's thought patterns at all. If this is emotional, then the emotional attachment to the continuity of the subjective experience seems to me equally valid. Otherwise, this should probably lead to a vast depreciation of the self.