Just watched "Looper", and it has a plot continuity-flaw.
The premise is that in the future it's impossible to kill someone without detection, such that they have to send targets back in time if you want them snuffed, yet a critical element of the motivation of one particular looper is that in the future, his girl-friend gets killed in front of him... in the age when it's supposed to be impossible to kill someone without liable detection.