Star Wars Episode 4: A New Hope - Which Side Does the Rank Really Go?
If you pay attention to the empeiral officers rank (the little red and blue squares on the uniform) in most of the scences they are on the left side. There are a few scences, like with the Grand Moff Tarkin and Vader, they appear on the right side.
This is because in a lot of the shots, they flipped the film in post production. It's most evident during the battle of Yavin, watch the pilot's microphones.
maybe the placement changees based on the individual's rank, duty assignment, etc. either that or this is the only safe form of defiance avilable to military personnel in a ruthlessly authoritarian society. perhaps the ones wearing it on the right are part of an underground group of rock fans groupies, tree-huggers or whatever. rock on!