If that prospect makes you a little uncomfortable, you are intuiting the problem of "pattern identity" vs "continuity identity".
Analogy: impregnating a woman and (eventually) causing her to give birth - that is, "duplicating" her, although the copy is actually not very like her - doesn't give you the right to kill her.
I'm fine with teleportation, if that's what you mean, but I go into that with the intention of the death of one of the copies. It's effective suicide, not externally-imposed murder.
What if one did this regularly? Would battle-hardened cloners become insensitive to "retirement" of their doppelgangers, or as the last survivor of the series of slayings would they start to feel hunted?
Really feels at least a few centuries too early to even gauge whether it is possible to substantially capture (let alone reproduce) the state of a brain. Sure would be disappointing if it turned out you could get 90% of the functionality with a ten-state DFA featuring frowning and pooping, but it would make cryonics a whole lot easier. "Just leave me enough brainstem to get home."
But I take it I am unusual in this.
I should think that such a circumstance would mean we wouldn't be able to copy a consciousness while being able to copy the mind. Of course, this would bring in to question exactly what person would mean.
What if the way to teleport was to make a copy of you at the new location, and then disintegrate the old you.
What has happened here, esp. wrt. consciousness? Is the copy really you? Is the old you OK with being disintegrated? What if the old you escapes, are there now two of you, and what does that mean? etc.
If he had gotten off the planet instead of me, don't you think he would have made the same choices that I made?
I always felt this line showed how disconnected Riker was about the situation. As if there actually were two of him on the planet before the transporter accident, and it was left to random chance which one of those two it was that left and which one stayed.
I would hope that that is indeed the case...
For people who are into anime, there is a very nice one about this issue called Kaiba [1] that envisions a future where everyone is freely able to modify their memories and swap them across bodies.
I think this is probably a bit misleading. I can't imagine de Grey being anything other than reductionist in his views about the mind, so I can only imagine his interpretation of this question to be as follows: "has the scanning process captured all the relevant information about the person's mind?" Have you created a new person (by missing out some information from the original's physical instantiation), one who is perhaps very similar to the original, but where some details are different because the scan was not of high enough fidelity?
Of course, it's still unknown whether it's even possible to extract sufficient detail from the brain; if by unhappy chance it turns out that some of the quantum details of the brain's state are important to the mind, then it's possible we may simply never be able to copy a person. Let us hope that is not the case.