I've seen places where some homeowner mounted the outlets upside down just for the hell of it. Seen places where the orientation is different in different rooms. There's a slight charge on some of the plumbing in the house I grew up in, probably because some fixture somewhere is wired backward, but no one has found the backward connection in 50 years. And my grandfather was an electrician, and my brother is a communications tech.
Then there are people who violate the Second Law of Plumbing, and put the cold on the left.