Public transport:
People who who don't have the patience or manners to wait and get on the bus at the front door. Instead they use the rear door and then while touching on with myki block the aisle for everyone who came through the front door.
Bus drivers who open the back door when no one's getting off.
People getting off the train who have travelled from zone 1 to 2, and touching off causing a huge blockage at the exit. If you travel from zone 2 to 1 in the morning, touching on and off, and then touch on again in zone 1 on your way home, you don't need to touch off again in zone 2. The system will charge you for a 1 and 2 daily anyway. A lot of these people then go and touch on and off the bus!