I think this is a reasonable idea.<p>However, you have a two sided market with a classic chicken and egg conundrum.<p>There are two solutions to this problem. The correct one is to provide value to one side of your market without requiring a match on the other.<p>You could offer celebrities a standard AMA hosting facility, if you can make your product somehow better than the alternatives. This seems hard.<p>Better is to focus on the kind of people who will visit to ask questions. Collect together links and content (preferably syndicate it) that relate to their heroes. So find all the AMA for a celebrity and throw together interview links and the best videos you can find into a fanpage. Then share your collection with fans on reddit etc. Once you have traffic, you collect questions, then contact your celebrity and ask them to do an AMA.<p>Focus on niches with dedicated fans without obvious destinations for this material. Promote. Rinse. Repeat.