I would define it as the strange feeling of discord when one's actions are not aligned with the expectations of society.

It may involve simple name calling (slut, bastard, etc) or socially unacceptable situations (public nudity) or acts (things which are 'sick').

For me personally, as a Dom, the thrill is the sense of self-empowerment, individualism and freedom. Having sex in a public place is unacceptable to society; thus, doing so snubs that control and defines me as ME, as my own wants and desires unfettered by others. I would imagine for a sub it would be similar but inverted: a sense of being totally controlled, individualism and importance as a result of surrender and lack of power.