The sharing economy, like all economies, is a system of exchange of goods and services. However, unlike the traditional economies, the sharing economy emphasizes peer-to-peer relationships, collaborative production, and barter rather than purchase. Some people do try to make a lot of money and large, profitable companies have emerged from the sharing economy; but, the motivations behind collaborative consumption are generally more altruistic. For example, participants have said that they take part in ride sharing or offer their unused belonging on Freecycle because it is good for the environment, or they allow the SETI project to use their computer's downtime because they like to contribute to scientific advancement.