"It's basically a way to make socially acceptable something we all kind of know is wrong."

It's about desire -- how much we are willing to deceive ourselves in the reckless pursuit of something forbidden.

The beauty of the five-second rule is that it is utterly pliable and that it is not about food so much as it is about yearning and disgust and gastronomic history and evolutionary wiring and the implicit social contract we make when we break (and drop) bread with other human beings.

See also another recent post about disgust.