In general, cartels are economically unstable in that there is a great incentive for members to cheat and to sell more than the quotas set by the cartel (see also Game theory). This has caused many cartels which attempt to set product prices to be unsuccessful in the long term. Publicly-known exceptions to this include the Organisation of Petroleum Exporting Countries (OPEC) petroleum cartel and the De Beers diamond cartel.

As its name implies, OPEC is organised by sovereign states. It escapes antitrust enforcement in other jurisdictions by virtue of the doctrine of state immunity under public international law.

Many trade organizations, especially in industries dominated by only a few major companies, have been accused of being fronts for cartels:

People of the same trade seldom meet together, even for merriment and diversion, but the conversation ends in a conspiracy against the public, or in some contrivance to raise prices.

Adam Smith, The Wealth of Nations