Linked from
The 18 pages that link to Free-rider problem, each with the reason it gives.
BoycottRelated: Boycotts can falter when supporters rely on others to bear the costs of abstaining.
Coase theoremRelated: Many affected parties can make bargaining costly and difficult to organize.
Public goods gameRelated: A noncontributor can enjoy the public good funded by others.
CustomerRelated: Some services have beneficiaries who are not identifiable paying customers.