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.

Unlike sharing, where the group is mainly an aggregate of participants, cooperating creates group identity.

[B]ecause the minimum costs of being an organization in the first place are relatively high, certain activities may have some value but not enough to make them worth pursuing in any organized way. New social tools are altering this equation by lowering the costs of coordinating group action.

[F]or any group determined to maintain a set of communal standards some mechanism of enforcement must exist.

Collaboration is not an absolute good.

Any system described by a power law [...] has several curious effects. The first is that, by definition, most participants are below average.