i just found this on someone's site......
An agency who intends to invest a great deal of time and money in you will want to ensure that their investment is protected. This is all business, afterall, even when the agent and the model/talent are the dearest of friends. Bills must usually be paid and overhead costs met. An agency, quite honestly, has a hard time making ends meet if they are not working hard all day long, every day, seven days a week. The payoff, of course, is when you find and develop (or sign) a major star. At that point, for instance, a 10% commission off a model or acting job or client contract that pays in the hundreds or millions of dollars can make an agency very comfortable financially. Then again, in smaller markets outside L.A. or N.Y., this is not always very likely. If an agency is legitimate, they must really have to enjoy what they do because it certainly is often not that rewarding when it's time to go do the banking.
In a "non-exclusive" contract, a model/talent is under less guidance and the agency may submit them, but generally is not breaking a major sweat to push them with a huge investment of time or resources. Just so this does not sound so bad, however, let me say that this does not imply the agency does not work hard for that individual. A good agency will treat everyone equal and present all potential talent to their clients, regardless of contract type agreement.
In an "exclusive" contract, the agency has more control over decisions and in the meeting of specific objectives. Wherein a non-exclusive deal the talent may be submitting for the same projects, or may have another agent doing this as well, in an exclusive agreement the agent has the upper hand and can better pitch you to the client because there is no confusion of possible multiple submission. If you have two agents submitting for the same thing for you, it can not only become confused... but it can often times cost you the potential job, audition, go-see, consideration, or interview.