DJ Khaled and Mayweather had an issue about shilling an ICO. And other celebrities hyping or promoting scam coins. Who would actually rely on their words? If you're listening to celebs then you are not ready for this type of market at all.
Basically they all get paid when doing promotions. That is a natural thing because usually they will not be too familiar with the procedures they are promoting, they are only brand ambassadors and when the project fails then we cannot blame them. The result is that the one who will continue to be responsible is the development team of the project.