I cannot think it is harmless. You have but to walk down an inner city street in a major city and see youths and young adults who are acting, talking, walking and thinking like rappers or like their favorite TV situational "comedy" star to see that there is harm in the cult of celebrity. This layer of harm is directed at observers and goes much deeper tha surface behavior with a direct correlation to at least some of the horrific events that have occurred in schools in recent years and decades.
The other layer of harm is toward the targeted individuals. It is hard enough to battle drug and alcohol abuses (Lindsay), disappointed careers (Hugh Grant), newly launched careers (Susan Boyle), horrible marriages (Princess Dana, as herappleness points out) and family adjustments to child's birth (Brook Shields) without being the target of inappropriate attention and merciless hounding. These individuals, and others like them, might have had easier roads and happier results if it hadn't been for cult fixations. This is speculation, true, but it is fair to say that without unwarranted anxiety, pressure, fearfulness, uneasiness (to state it mildly), anyone has an easier time of it and performs and succeeds better in life, so the speculative conditional of the harm done to targeted person is overridden by real-life probability.