I do, even though I know I shouldn't. I really don't give the washer a second thought, as it is in the basement and about 3 feet away from it, there is a floor drain.
Obviously, the dryer is a hazard, so I usually don' t leave it going while I leave the house, but honestly, it is in the basement, and if I'm upstairs, it could be on fire for a while before I notice. I do clean out the pipe religiously with the special tool every month, so I'm not that worried about it.
The dishwasher I don't worry about either, normally I set it to run as I am going to bed because it is so loud I can't stand to sit in the living room next to it while it is running.