I am currently writing a 18 days email sequences that sell an affiliate product in a relationship niche. The target market is mainly women. Originally, I quote some YouTube video as my content for the email, and those video are mainly from Tony Robbins. Nothing wrong with that, he is a good relationship coach, almost everybody in U.S. know him. But if you think there is nothing wrong with that, you are WRONG! When you are using celebrity, I think one of the way to approach this is to use a celebrity that your market admire and follow. Tony Robbins is great, but since most of my market are women, I choose Oprah Winfrey instead of Tony Robbins. For a women, I think Oprah will have a more "close" relationship then Tony. Look at their audience: Tony's event will have 1/2 men 1/2 women. And then look at Oprah show: 90% (or even more) women! Oprah talks to women, and my market is for women. Oprah is therefore much more appropriate then Tony. Hope it helps someone.