Humans are hard-wired to create mental shortcuts based on their previous experiences and observations. Stereotypes, cultural archetypes and expectations all result from the assumption that past observations are prologue to future experience. Too many times these stereotypes are negative and predispose a person to having a bad experience. But, occasionally these negative expectations are defied in such a way the outcome is exactly the opposite of what you expect—the result is a sense of surprise, joy and happiness.

This is the reason Susan Boyle, and Paul Potts before her, became instant internet celebrities. They defied the stereotypes we associated with their professions and surprised the world with their immense talents. Had Paul Potts grown up in Rome, looked comfortable on stage and sported a tuxedo, the world wouldn't have been so thunderstruck. If Susan Boyle looked more like a diva and less like a small town church singer, then tears wouldn't have welled up in the eyes of the millions who watched her performance.

It was the element of surprise that led to such intense emotions in the viewing audience. By defying the archetype we associated with their skills, they created an exceptional experience. The unexpected was where the power of their performance derived.

This has a use in marketing as well. Think about how you can defy expectations and create a positive surprise in the user experience. Maybe it's as simple as a better error page that makes people laugh, or instead of 5 day shipping, automatically ship everything overnight (it works for zappo's).

In the end, the expected positive experience will never be as powerful as the unexpected one.