Writing Excuses

Let's get back to world-building, and dig into a tough one: government. In this case we're talking about government as part of the backdrop, rather than political intrigue as part of the plot. Are you going to create a monarchy, a democracy, or perhaps some crazy, experimental sort of rigidly constitutional representative republic? City-states? Confederations? Empires? What's it going to be, and (more importantly) why? Oh, and how do you do it right? Writing Prompt:  Create a government by starting with "Colon Cleansers," and then taking two steps back to create something unique.