I get very frustrated when very basic aspects of the game are umpired poorly. If they can't get the basics correct, how can they handle the line-ball decisions?
For example, Jetta takes a mark in the MCC pocket, city end in the 2nd qtr. He turns around and walks back to take the shot on goal, but walks towards the centre to open up the angle, thus never being behind the mark (no problem with that, you have to have a crack at opening up the goal). He then plays on and kicks an easy goal. Strangely enough, the ump was yelling no, no, no when he took off, then signalled all clear. It's such a basic rule that you have to be behind the mark before you can play on. He probably would have kicked the goal anyway, but you never know.
Small point I know, but a real pet peeve of mine.