On the exclusivity of speakers

An interesting discussion popped up today at the headquarters of the Chinabiz Speakers. In my talks with current or potential speakers I would not bring up the matter of exclusivity. In my view we first have to proof we can bring in some business for our speakers and then, down the road, we might discuss the issue with a core group of our speakers. At least, that was my opinion.
From our speakers we sometimes get different signals and a few of the top-speakers now actually demand that we are going to represent them exclusively. How does that work?
In our preparation phase we have mainly been trying to work out how companies, organizations and event organizers manage their workflow and how we can add value to that process. We have underestimated the problems much-wanted speakers have in managing their assignments.
Even speakers with a long track record have more to do than manage their speaking career. They often have a job, other work, children to take care off. Some just do not like to work too hard. Some of them are so busy in saying no to invitations or suggesting other speakers, that they would love to outsource that work.
Well, our lawyer is now drafting a contract for exclusive speakers. Main problems is defining the scope of our work. Most of our speakers sometimes have to give also speeches for free, for example because it is part of their work. Drawing a line between those unpaid obligations and paid-for activities is rather simple in the domestic academic work, but a bit harder in the commercial world.