One at a time please
While the prospect of uploading our minds into supercomputers remains a distinct possibility, it's an open question as to whether or not we'll also be capable of transferring our consciousness as well. Most uploading schemes describe the copying of neural information from biological to digital substrate — but what's often lost in the conversation is the question of how a person can suddenly be in two places at once. Destructive copying (similar to the teleportation problem), will still result in a perfectly replicated person who will adamantly insist that they're the genuine thing — but so would the other 50 copies. As for the original source consciousness, it would cease to exist. This is what's referred to as the "continuity of consciousness problem," and it's a matter of great contention in the philosophical, neuroscientific, and AI communities. Part of the problem is that we still don't have a developed science to explain the nature of consciousness, so we're left guessing. As futurist John Smart told io9, it's likely an issue that will never be satisfactorily resolved. "This is an issue that will eventually start to take on religious or spiritual connotations," he said, "people will just have to take a leap of faith and make the jump."