Hmm. I bet people think it's Ben Affleck because the writing style is similar to the way he talks. But then again, it's easy to imitate Ben Affleck, so it could just be a red herring.
My guess is that it's probably somebody you'd never expect. Although I could totally see George "Mr. I-don't-want-to-play-the-game-I-want-to-do-things-my-own-way" Clooney doing this.