Pyramid schemes.

A business model that involves the exchange of money for enrolling people into the scheme. Pyramid schemes, often referred to as multilevel marketing (MLM) or network or matrix schemes, work by offering distributorships without product. The company promises, that once has signed up as a distributor, one will receive commissions for sales and recruitment for new members. However, the plan collapses once new distributors cannot be recruited, so those at the bottom levels inevitably lose money.