One of the most compelling cultures Graeber profiles is the Tiv of West Africa, who have very particular rules about exchange. For starters, they believe that bringing an economic transaction to full completion is essentially immoral, or at least frowned upon, because it implies that one party doesn’t want anything to do with the other in the future. If a Tiv man or woman gives you a gift, you are supposed to respond with another gift of slightly greater or lesser value. The outstanding debt between the two of you is a signal that your relationship is going to continue. To respond with a gift of equal value would be to say implicitly that you wish to even things out and draw your relationship to a close.
Rob Trump: Why would you ever give money through Kickstarter? in: nytimes.com, 2013-02-08.