People who benefit from a resource while doing nothing in recompense are free riders. Societies have generally dealt with the problem of free riders in one of two ways.

The first way is the elimination of commons, transferring ownership of parts of it to individuals, all of whom have an incentive to protect their own resources.

If six shepherds each own one-sixth of the former commons, the overgrazing problem is a personal one, not a social one. If you overgraze your section, you will suffer the future consequences, while your neighbor will not.

The second way is governance or, as Hardin puts it, 'mutual coercion, mutually agreed upon.' This solution prevents the individual actors from acting in their own interests rather than in the interests of the group.

Now that group forming has gone from hard to ridiculously easy, we are seeing an explosion of experiments with new groups and new kinds of groups.

Sharing creates the fewest demands on the participants. Many sharing platforms, such as Flickr, operate in a largely take-it-or-leave-it fashion, which allows for the maximum freedom of the individual to participate while creating the fewest complications of group life.

Cooperation is the next rung on the ladder. Cooperating is harder than simply sharing, because it involves changing your behavior to synchronize with people who are changing their behavior to synchronize with you. Unlike sharing, where the group is mainly an aggregate of participants, cooperating creates group identity - you know who you are cooperating with. Conversation creates more of a sense of community than sharing does, but it also introduces new problems.

Collaborative production is a more involved form of cooperation, as it increases the tension between individual and group goals. Structurally, the biggest difference between information sharing and collaborative production is that in the latter at least some collective decisions have to be made.

Collaborative production can be valuable, but it is harder to get right than sharing, because anything that has to be negotiated about, like a Wikipedia article, takes more energy than things that can just be accreted, like a group of Flickr photos.

Collective action, the third rung, is the hardest kind of group effort, as it requires a group of people to commit themselves to undertaking a particular effort together, and to do so in a way that makes the decision of the group binding on the individual members.

All group structures create dilemmas, but these dilemmas are hardest when it comes to collective action, because the cohesion of the group becomes critical to its success.

Information sharing produces shared awareness among the participants, and collaborative production relies on shared creation, but collective action creates shared responsibility, by tying the user's identity to the identity of the group.

In historical terms, a potluck dinner or a barn raising is collaborative production (the members work together to create something), while a union or a government engages in collective action, action that is undertaken in the name of the members meant to change something out in the world, often in opposition to the other groups committed to different outcomes.

The commonest collective action problem is described as the 'Tragedy of the Commons', biologist Garrett Hardin's phrase for situations wherein individuals have an incentive to damage the collective good.

The Tragedy of the Commons is a simple pattern to explain, and once you understand it, you come to see it everywhere. The standard illustration of the problem uses sheep.

Imagine you are one of a group of shepherds who graze their sheep on a commonly owned pasture. It's obviously in everyone's interest to keep the pasture healthy, which would require each of you to take care that your sheep don't overgraze. As long as everyone refuses to behave greedily, everyone bebefits.

There is just one problem with this system: 'everyone' doesn't take your sheep to market. You do. Your incentive, as an individual shepherd, is to minimize the cost of raising the fattest possible sheep. Everyone benefits from you moderating your sheep's consumption of grass, but you would benefit from free riding, which is to say letting them eat as much free grass as they possibly could.

The minute one of the other shepherds keeps his sheep out in the pasture an hour longer than necessary, the only power you have is to retaliate by doing the same. And this is the Tragedy of the Commons: while each person can agree that all would benefit from common restraint, the incentives of the individuals are arrayed against that outcome.