Normally, it is not easy to counteract usurers (uitbuiters / woekeraars). An usurer has something that is very much needed by someone else, and can therefore ask a very high price. In the Air Traffic Management sector, usury can be a problem. Many people are advocating the use of market mechanisms in Air Traffic Management. But an airline should not be able to sell a slot against an usurious price.
The Spender-signed Currency System makes it possible to counteract usurers. In this currency system, every user must sign every credit it uses. Value of a credit is determined according to the signatures on it. Using these credits, agents can work together to counteract an usurer.