Of course, just because psychics have not been able to find missing persons doesn't mean that they might not have other psychic abilities. It's important to keep an open mind, and try to demonstrate psychic powers in an objective, scientific manner, under conditions that rule out deception.
The Million Dollar Challenge has been around for many years. Some psychics have claimed that the money does not really exist (as part of a Nightline primetime special that aired Friday, ABC News verified that the money is real and available, held in trust by a third party).
Others have suggested that psychics would not use their powers for personal gain (they should check out the ticket prices for appearances and workshops by some of these celebrity psychics), though of course the winning psychic could donate the $1 million to charity.
Will these celebrity psychics take Randi's challenge? If they have the powers they claim, and can demonstrate them under scientific conditions, they have nothing to lose.
In fact, the publicity of having their abilities validated would likely raise their profiles even higher (to say nothing of the satisfaction they would get from publicly proving the skeptics wrong).
Either the psychic information they give is accurate, or it isn''t; there's no real way that skeptics could disprove genuine psychic powers. If the psychics have the powers they claim, they have nothing to lose and $1 million to gain.