If you give a gift that can never be repaid, you're making a statement about personal power. You're saying that, like a child, the receiver is potentially at your mercy. You are bragging, and that can rankle whoever you're bragging to. And when you insult them, there's a good chance they will want to retaliate.
So your "gift" can start a fight.
Every society has addressed this problem. In highly populous societies, gift-giving arrogance is not a severe problem. Such societies solve their problems through a system of established rights (not necessarily justice). Each individual in the populous society is apportioned rights. These might be the radically differing classist rights of king and peasant or the common rights of our own democracy. One way or another, rights solve the gift-giving difficulties.
In our own society, for example, one of our common rights is that of an individual to make as much money as desired. An individual then has the right to spend his money in any way he sees fit. If he wishes to lord himself over someone else by buying them an outrageously expensive gift, he has the right to do so. The only say the receiver has in the matter is whether or not to accept it; it isn't illegal to refuse. But mostly, we've adapted our society to the reality of the situation: - anyone can buy anything they want, and if they want to give it to you, you might as well take it.
While I've personally heard of those too proud to accept a gift, the general modern sentiment is that one should always accept. Hence the saying, "Never look a gift horse in the mouth." This expression supposes that any gift is worth having, and only a fool rejects that which is free.
In societies that are more hierarchical than ours in which the individuals are ranked or set into classes, gift-giving becomes less of a personal gesture and more of an assertion of status. One cannot afford to abstain from gift-giving. If one does not give gifts to social inferiors, one runs the risk of looking stingy, thus weak. In Europe's Middle Ages, a time of feudalism, with peasants under knights under lords under kings, gift-giving was a tool of warfare as surely as a sword. Those of high social status were under constant scrutiny by others ready to displace them, and lavish gift-giving was a way of demonstrating to watchful eyes that you were doing well: - you had resources to spare, which meant you were still strong.
The Indians of North America's Northwest Coast - Haida, Tlingit, Kwakiutl, Salish and over two dozen other tribes - developed an elegant system suited to their rank-based societies. They had a number of related ceremonies that have by today blurred into one another, collectively known as the "potlatch" tradition (the term is a generalization applied by white traders, and derives from the Chinook trade jargon). The potlatch is a grand festival in which there is a flow of gifts from the top of the social hierarchy to the bottom. He who can give the richest gifts - always the chief - gives out to those immediately below him in rank. They give to those below them. And so this trickle of wealth continues until it reaches those at the very bottom of the social scale (who, in olden days, were just above the level of slaves).
This tradition functions as an official system of wealth distribution, but also as a distribution of pride, and an assertion of status. It is the method by which the more powerful display their might to the less powerful, and thereby verify their station. In this way, social order is preserved, and every ego at the potlatch is stabilized. You may have had someone show off to you, but at least you got to show off to someone else. The only ones who lose out in terms of pride are those at the very bottom, but at least they come away with lots of goodies. They're the ones who would benefit most from the saying about gift horses...
Now, as I said before, these sorts of systems work fine for the larger societies. But what about those smaller societies, where everyone is supposed to be a social equal? What if there is ego, arrogance, without rank?
(Next: Kaliai, !Kung, and Inuit.)