Joshua Abraham Norton (1818-1880) was a San Francisco investor until he was rendered bankrupt in 1859. Psychologically unstable but colorful, he took up himself the role of Emperor of the United States of America and Protector of Mexico. The natives of the city humored him, printed his proclamations in the newspapers, and permitted him to support himself by selling 'promissory notes', which are now worth many times their original value.
The notes Emperor Norton issued were accepted as money at many businesses in San Francisco. His positive comments on a restaurant were a great way to improve that restaurant's business.