iStarter made a study about celebrity endorsement equity:
Celebrity endorsement equity is the new way for celebrities to advertise and support startups trough social medias. They will offer their visibility (e.g. their follower base) in exchange of equity: a smart way to invest with small risks and potential huge returns.
There are some example like 50cent who joined in Vitamine Water when it was at the beginning, when he received the shares their value was 5 million, when 50cent made the exit deal the shares’ value was of 100 million, so he made a return of +2000%, now you can see what is Vitamine Water