The general rule in Illinois is that, in the absence of an express contract, a taking of a customer list, or fraud, a former employee may not properly be enjoined from soliciting his former employer’s customers whom he served during his employment. An Illinois court has stated:
Our free economy is based upon competition. One who works for another cannot be compelled to erase from his mind all of the general skills, knowledge, acquaintances and the over-all experience which he acquired during the course of his employment. The success of a person who is engaged in sales depends largely upon his personal friendships and the confidences inherent therein. Absent special circumstances, such persons cannot be prevented from seeking out customers of his former employer when he has entered into a competing business or gone to work for a competitor. If a salesman has agreed to a restrictive covenant in his employment contract, or if he has fraudulently and surreptitiously copied or removed lists of customers from a prior employer or if the names of actual or potential customers are confidential, not subject to memory, are not publicly listed or otherwise readily obtainable, then, under proper circumstances, such salesman might be enjoined from soliciting business from the customers of his prior employer. Absent such circumstances, however, there can be no such prohibition.