Employment contracts give a principal the authority to decide flexibly which task his agent should execute. However, there is a tradeoff, first pointed out by Simon (1951), between flexibility and employer moral hazard. An employment contract allows the principal to adjust the task quickly to the realization of the state of the world, but he may also abuse this flexibility to exploit the agent. We capture this tradeoff in an experimental design and show that principals exhibit a strong preference for the employment contract. However, selfish principals exploit agents in one-shot interactions, inducing them to resist entering into employment contracts. This resistance to employment contracts vanishes if fairness preferences in combination wi...