People who just leave used mugs, plates, cutlery, bowls and any other kitchen ware in or next to the sink at work when the dishwasher is below the counter next to it. Do they do this at home? Do they expect other people to put it in their for them? Is their intention to return to it later? Leave it for the cleaner?
Most annoying is when people fill their mug with water then leave it in the sink making it even more annoying to move them if the sink is needed.