I remember when Looper had just come out, it kicked up such a **** storm of arguments over plot holes (reasonably so). I love the movie to death and have re-watched it a couple of times since its release, enjoying it just as much each time, but I don't think I can remember another time where a universally acclaimed movie left so many questions up in the air for so long. That plot hole you're talking about above seems quite minor in comparison to some of the Looper complaints I've read.
Here's one for Looper I see a lot: