In the Movie industry agents are a must if you're a hot commodity. They take a percentage of what they can get for you, so the more they get you, the more they get. If you're sort of hot or pretty decent then what they can get for is part of a dynamic whereby they maintain good relations with the Studios/Producers so that they can continue to make a living until the next superstar comes there way. But if you don't know how to realistically judge your own value, as well as a particular Studio/Producer's budget then agents are a very necessary evil. Not to mention the buffer they provide during negotiations, because if you were the one playing hardball to get the rate you wanted it will probably leave a bad taste in the mouths of several key players.