In my opinion, a celebrity or artist does not matter and is not appropriate to endorse crypto currencies. One of the characteristics of the crypto currency is anonymous so our real identity can be guaranteed. When a celebrity or artist endorses so it is dangerous for himself. Security will threaten him. Indeed crypto currencies are best promoted through bounty campaigns. I myself am a contender who is not a celebrity or artist if given a job to endorse certain crypto currencies so I choose not to accept the job. The job can be very risky because our name can be misused. That's the most dangerous. Okay, that is a bit of my idea.