In this model, public goods can be distinguished by their nonexclusivity and lack of rivalry, thus all within a polity will benefit from their provision regardless of individual contributions to the cost of the good. Because of this, little utilitarian incentive exists for the individual to contribute, and public goods will be supplied in suboptimal quantities unless individuals are coerced or given selective incentives to contribute. The model has been applied to defense policy, lobbying, and the formation of labor unions. While within guerrilla alliances, collective war-making may be seen as a collective good subject to the free-riding common to such goods, the same may not be quite so true of terrorist alliances. Typically, terrorists are motivated by purposive aims. Such terrorism holds great risks and no material rewards and usually is employed as a means of altering government policies rather than defeating a determined enemy. Coalitions are unlikely to occur, and if they do occur, they are likely to be attempted in a contractual manner. If coalitions do occur, no partner will seek to avoid activity, for participation itself is the goal -- whatever the cost. The organization of interests within such terrorist groups has implications for coalitions, free-riding, and betrayal to state authorities that provide clues for combatting terrorism. 27 notes.