Funny that you mentioned this. Just the other day, I watched an episode of star trek voyager where Tuvok and Nelix were involved in a transporter accident that fused the two together. The entire episode was about the crew getting used to the new person that was a combination of the two crewmen. Finally, at the end of the episode they found a way to separate them again. But the new crewman didn't want to go through with the procedure. He did not want to "die". In the end, Janeway had to force him to go through with the procedure, which he described as "murder".
This is an issue that, I suspect, has many implications that most people just simply don't want to tackle. We must first define what a person is and isn't. Since there is no fine line, there will undoubtedly be varying opinion on this matter.
As for me, I'm staying neutral on this topic.