1) Imperfect information: e.g. supplements that perhaps have no effect but there's no evidence, or product that does harm but does not need to repeat business with the same consumers
2) Companies that exploit irrationality: e.g. lottery
3) products may advantage the consumer over other people in zero-sum or negative-sum games: e.g. a company that sells software that helps you spam people
4) negative externality: e.g. pollution
(source: <a href="https://80000hours.org/2017/10/spencer-greenberg-social-science/">https://80000hours.org/2017/10/spencer-greenberg-social-science/</a> (2018-02-11))