Human beings are social creatures—not occasionally or by accident but always. Sociability is one of our lives as both cause and effect. Society is not just the product of its individual members; it is also the product of its constituent groups. The aggregate relations among individuals and groups, among individuals within groups, and among groups forms a network of astonishing complexity. We have always relied on group effort for survival; even before the invention of agriculture, hunting and gathering required coordinate work and division of labor. You can see an echo of our talent for sociability in the language we have for groups; like a real-world version of the mythical seventeen Eskimo words for snow, we use incredibly rich language in describing human association. We can make refined distinctions between a corporation and a congregation, a clique and a club, a crowd and a cabal. We readily understand the difference between transitive labels like "my wife's friend's son" and "my son's friend's wife, " and this relational subtlety permeates our lives. Our social nature even shows up in a negation. One of the most severe punishments that can be meted out to a prisoner is solitary confinement; even in a social environment as harsh and attenuated as prison, complete removal from human contract is harsher still.

Our social life is literally primal, in the sense that chimpanzees and gorillas, our closest relatives among the primates, are also social. (Indeed, among people who design software for group use, human social instincts are sometimes jokingly referred to as the monkey mind.) But humans go further than any of our primate cousins: our groups are larger, more complex, more ordered, and longer lived, and critically, they extend beyond family ties to include categories like friends, neighbors, colleagues, and sometimes even strangers. Our social abilities are also accompanied by high individual intelligence. Even cults, the high-water mark of surrender of individuality to a group, can't hold a candle to a beehive in terms of absolute social integration; this makes us different from creatures whose sociability is more enveloping than ours.

This combination of personal smarts and social intuition makes us the undisputed champions of the animal kingdom in flexibility of collective membership. We act in concert everywhere, from simple tasks like organizing a birthday party 9itself a surprisingly complicated task) to running an organization with thousands or even millions of members. This skill allows groups to tackle tasks that are bigger, more complex, more dispersed, and of longer duration than any person could tackle alone. Building an airplane or a cathedral, performing a symphony or heart surgery, raising a barn or razing a fortress, all require the distribution, specialization, and coordination of many tasks among many individuals, sometimes unfolding over years or decades and sometimes spanning continents.

We are so natively good at group effort that we often factor groups out of our thinking about the world. Many jobs that we regard as the province of a single mind actually require a crowd. Michelangelo had assistants paint part of the Sistine Chapel ceiling. Thomas Edison, who had over a thousand patents in his name, managed a staff or two dozen. Even writing a book, a famously solitary pursuit, involves the work of editors, publishers, and designers; getting this particular book into your hands involved additional coordination among printers, warehouse managers, truck drivers, and a host of others in the network between me and you. Even if we exclude groups that are just labels for shared characteristics (tall people, redheads), almost everyone belongs to multiple groups based on family, friends, work, religious affiliation, on and on. The centrality of group effort to human life means that anything that changes the way groups function will have profound ramifications for everything from commerce and government to media and religion.

One obvious lesson is that new technology enables new kinds of group-forming. The tools Evan Guttman availed himself of were quite simple—the phone itself, e-mail, a webpage, a discussion forum—but without them the phone would have stayed lost. Every step of the way he was able to escape the usual limitations of private life and to avail himself of capabilities from various professional classes to the general public is epochal, built on what the publisher Tim O'Reilly calls 'an architecture of participation."

When we change the way we communicate, we change society. The tools that a society uses to create and maintain itself are as central to human life as a hive is to bee life. Though the hive is not part of any individual bee, it is part of the colony, both shaped by and shaping the lives of its inhabitants. The hive is a social device, a piece of bee information technology that provides a platform, literally, for the communication and coordination that keeps the colony or from their shared, co-created environment. So it is with human networks; bee hives, we make mobile phones.

But mere tools aren't enough. The tools are simply a way of channeling existing motivation. Evan was driven, resourceful, and unfortunately for Sasha, very angry. Had he presented his mission in completely self-interested terms ("Help my friend save 4300!") or in unattainably general ones ("Let's fight theft everywhere!"), the tools he chose wouldn't have mattered. What he did was to work out a message framed in big enough terms to inspire interest, yet achievable enough to inspire confidence. (This sweet spot is what Eric Raymond, the theorist of open source software, calls "a plausible promise.") Without a plausible promise, all the technology in the world would be nothing more than all the technology in the world.

As we saw in the saga of the lost Sidekick, getting the free and ready participation of a large, distributed group with a variety of skills—detective work, legal advice, insider information from the police to the army—has gone from impossible to simple. There are many small reasons for this, both technological and social, but they all add up to one big change; forming groups has gotten a lot easier. To put it in economic terms, the costs incurred by creating a new group or joining an existing one have fallen in recent years, and not just by a little bit. They have collapsed. ("Cost" here is used in the economist's sense of anything expended—money, but also time, effort, or attention.) One of the few uncontentious tenets of economics is that people respond to incentives. If you give them more of a reason to do something, they will do more of it, and if you make it easier to do more of something they are already inclined to do, they will also do more of it.

Why do the economics matter, though? In theory, since humans have a gift for mutually beneficial cooperation, we should be able to assemble as needed to take on tasks too big for one person. If this were true, anything that required shared effort—whether policing, road construction, or garbage collection—would simply arise out of the motivations of the individual members. In practice, the difficulties of coordination prevent that from happening. (Why this is so is the subject of the next chapter.)

But there are large groups. Microsoft, the U.S. Army, and the catholic Church are all huge, functioning institutions. The difference between an ad hoc group and a company like Microsoft is management. Rather than waiting for a group to self-assemble to create software, Microsoft manages the labor of its employees. The employees trade freedom for a paycheck, and Microsoft takes the cost of directing and monitoring their output. In addition to the payroll, it pays for everything from communicating between senior management and the workers (one of the raisons d'etre for middle management) to staffing the human resources department to buying desks and chairs. Why does Microsoft, or indeed any institution, tolerate these costs?

They tolerate them because they have to; the alternative is institutional collapse. If you want to organize the work of even dozens of individuals, you have to manage them. As organizations grow into the hundreds or thousands, you also have to manage the managers, and eventually to manage the managers' managers. Simply to exist at that size, an organization has to take on the costs of all that management. Organizations have many ways to offset those costs—Microsoft uses revenues, the army uses taxes, the church uses donations—but they cannot avoid them. In a way, every institution lives in a kind of contradiction: it exists to take advantage of group effort, but some of its resources are drained away by directing that effort. Call this the institutional dilemma—because an institution expends resources to manage resources, there is a gap between what those institutions are capable of in theory and in practice, and the larger the institution, the greater those costs.

Here's where our native talent for group action meets our new tools. Tools that provide simple ways of creating groups lead to new groups, lots of new groups, and not just more groups but more kinds of groups. We've already seen this effect in the tools that Evan used—a webpage for communicating with the world, instant messages and e-mails by the thousands among his readers, and the phone itself, increasingly capable of sending messages and pictures to groups of people, not just to a single recipient (the historical pattern of phone use).

If we're so good at social life and shared effort, what advantages are these tools creating? A revolution in human affairs is a pretty grandiose thing to attribute to a ragtag bunch of tools like email and mobile phones. E-mail is nice, but how big a deal can it be in the grand schem...