... is that they are prone to the same problems as any other celebrities:
1. Grandiosity of imagining that they are experts in things way outside their fields. Watch this clip of Tom Cruise speaking about how he understands the history of psychiatry. He's making huge claims about his knowledge. Celebrity preachers can do the same (though, thankfully, not to this extent!) MD, for example, is an expert in household management, children's nutrition, natural heath stuff, raising children, sex, personal finance and wealth creation, leadership, Australian culture, Sydney anglicanism, the UK church scene, UK culture, theological education...
2. Thinking that they are truly exceptional and so believing they are entitled to special treatment from others - no criticism etc. This can make them awful to work with.
3. Obsession with with self - notice how much a celebrity/celebrity preacher talks about themselves. In anyone else we would think it obscene.
Humility is hard for us all. For the celebrity it's 100x harder.