Dishwashers have three states: empty, dirty dishes, clean dishes. The first state is hypothetical. Distinguishing between the dirty and clean states is not always obvious. Putting some dirty dishes into a machine with clean ones can soil the clean ones. This can lead into discussions with the significant other.
A solution would be for dishwasher makers to install a mutual exclusion device to the dishwasher: a button that says "dirty" until the dishwasher runs, at which point the buttons changes to say "clean", and stays that way until you press it.
Whoever removes the empty dishes from the machine presses the button, which changes to say "dirty".
Edit: Old discussion page.