...among people who design software for group use, human social instincts are sometimes jokingly referred to as "the monkey mind."
In his book The Upside of Irrationality, Dan Ariely, a behavioral economist at Duke University and one of the most interesting and popular writers on the subject, describes an experiment involving two chimps placed in neighboring cages, with a table of food just outside the cages but still within their reach. The food table is wheeled, and either chimp can reach out to pull the table closer to its own cage (and farther from the other's). However, a "revenge rope" leading out from each cage is connected to the bottom of the table, rigged so that if either chimp pulls it the table will collapse and spill all the food onto the floor and out of reach for both of them. Researchers have found that if both chimps share the food, all goes well in this experiment. But if one chimp rolls the table too close to its own cage, the other will sometimes explode in a rage and yank the rope, collapsing the table. According to Ariely, "The urge to punish exists in animals, too....The similarity between humans and chimps suggests that both have an inherent sense of justice and that revenge, even at personal expense, plays a deep role in the social order of both primates and people."
One way to understand the ebb and flow of interaction among people in a social group is to step back and treat the group itself as a kind of system. A system is a collection of individual "parts that work together by way of some driving process," to quote just one typical definition. A school of fish, a galaxy of stars, a hydroelectric dam, the economy of Spain, the global climate, a software application, a beehive - all these are systems, and they can each be broken into individual parts that work together through some overall set of processes.
The behavior a system exhibits to an outside observer "emerges" from the individual actions of its various components, whether these components are bees in a hive, or stars in a galaxy, or buyers and sellers in a market. Interactions between components generate feedback loops that tend to govern the overall behavior of the system itself. Negative feedback loops slow things down, while positive feedback loops speed things up. A thermostat is the classic example of a negative feedback loop. The closer the temperature gets to where you set the thermostat, the less heat or air conditioning the "system" will call for. A bank run, on the other hand, is the result of a positive feedback loop, because the more people go into the bank to take their money out, the more others will also want to do so.
The network of people who interact on a social media site make up a system also, and this system is driven by feedback loops that tend either to increase or diminish the influence of individual participants. It takes all kinds to build a sustainable, prosperous society. Trustability is important, but the willingness to punish untrustable behavior is also vital, and serves as an indispensable feedback loop for many social-group systems.
According to Nicholas A. Christakis and James H. Fowler, authors of Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives, Wikipedia works well because over time a social community of interested contributors develops to participate in fashioning the most authoritative entry for each topic. The majority of these participants are what Christakis and Fowler call "cooperators." They are the people who do most of the work that lies behind Wikipedia's success as a reference tool. By contributing new thinking, writing, and editing, cooperators help others to jointly produce and refine articles in their subject area of expertise. But in addition, the Wikipedia crowd will include a number of "free riders" - people who, in the authors' words, "want to use the credibility of the information established by others for their own purposes." A free rider might highjack a particular Wikipedia entry to publicize himself, or to paint a favorable view of his own company, or perhaps to advance a biased perspective on some politically charged or controversial issue.
What keeps free riders in check, however, and what sustains Wikipedia as a viable example of genuine social production, is the fact that there are literally thousands of "punishers" patrolling various Wikipedia entries. These folks may or may not have contributed their own material at some point, but they take umbrage at the offenses committed by the free riders. Punishers take it upon themselves to control the damage done by free riders - by reversing inappropriate, biased, or inadequately supported entries, by posting chastising notes on the personal "talk" pages of individual free riders, and even (in collaboration with other contributors) preventing some egregious offenders from making further contributions. It is the balance between creating, sharing, and punishing that makes Wikipedia both stable and useful, as a system.
What this all means is that in order for a "culture of sharing" to develop in a social group, it isn't necessary that 100% of a group's members be absolutely trustable. Sharing and collaborating strengthen a group's overall level of trustability, while punishing untrustable behavior sets up a feedback loop to maintain it. So the trustability ethos can develop and flourish in a social group, and can create immense economic value, as long as the "system" contains the right balance of cooperators and punishers, ensuring that free riders are held in check and not allowed to undermine things.