Reciprocation is so powerful that some people will risk everything and willingly break the law to repay a favor:
Mr. Kumar said he initially rejected Mr. Rajaratnam’s offer, explaining that McKinsey would not allow the separate arrangement. But Mr. Rajaratnam persisted. “People are making fortunes,” he recalled Mr. Rajaratnam saying. “So just keep track of your knowledge and share it with me.”
Mr. Rajaratnam also devised a scheme to hide the arrangement from McKinsey. He suggested that Mr. Kumar open a Swiss bank account in someone else’s name. Mr. Rajaratnam also proposed that the money paid to Mr. Kumar should be re-invested in a Galleon fund in the name of Mr. Kumar’s housekeeper.
Mr. Kumar capitulated, and in 2003 began to pass tips about his clients to Mr. Rajaratnam. “I felt an obligation to try and help him” once he began paying me, Mr. Kumar said.
Reciprocation is the act of returning a favor. You can learn more in Robert Cialdini's book: Influence: The Psychology of Persuasion.