Dirty dishes - Do you leave them overnight?

I live with a couple and they would always leave their dirty dishes overnight on the sink. This doesn't really bother me, but sometimes it can be an inconvenience if I need to wash something on the sink. This however got me into thinking about people's habits when it comes to doing their dishes. Do you wash your dishes every meal or do you let it pile up before you clean up? Do you clean up everynight and leave the kitchen neat and tidy before turning off the lights, or you let the dirty dishes soaked overnight? Do you wash them by hand or do you throw them in the dishwater?