i work in 'washroom product sales' and the reason to get upset about the seat being left up, is because of something called 'the sneeze' effect. When the toilet flushes, if the seat is up, tiny microscopic particles of ecoli, bacteria and faecal matter spray outwards and upwards into the bathroom area, coating everything from the seat to the sink, to your toothbrush if left out, and even the door handle. So everyone should close both lids before flushing or risk scrubbing your teeth with nasty germs!!!!