I don't see what the issue is, as long as they use that bar thingy to separate their items from yours. I do this all the time. Either I have just a few items that I'm holding in my hands and want to set them down before I accidentally drop them, or I've got my cart filled and want to speed up the check-out process by getting them on the conveyor belt. I guess I could see if there wasn't that separator bar or not enough space to put the items on the counter / belt. And in those few cases, I'll patiently wait. But that is pretty rare when I feel that unloading my own items will inconvenience the person ahead of me...