Here is a recent story about two professional mediums who failed to demonstrate their abilities in a laboratory setting.
Professional mediums and psychics are usually non-reader or subtly aware reader entertainers and performers. Instead of paying attention to the other readers around them they thought they were special and became professionals and began offering these services to others (non-readers who take them seriously or readers who only go for entertainment). The only problem with this is as soon as these subtly aware readers try to demonstrate their abilities in a laboratory setting or in a way that truly provides solid evidence, their abilities fade away. If they are more than a subtly aware reader then the consequences are more severe. High level readers that demonstrate their abilities in a performance manner are required to tell everyone that it is all a trick. Real readers will repeat over and over that they are only using tricks while demonstrating their abilities because it is the rule to never discuss the secret outside of the telepathic connection.