What about people that are buying used phones? What's to stop the owner to claim their phone was stolen after the sale?
Assuming some type of police report is required to start this process, I would think the fact that filing a false police report is a crime would be the deterrent to stop people from doing that. I certainly hope that a person can't just walk into AT&T and say "my phone was stolen" and AT&T just adds it to the system based on their word.