Here's my take:
Is a Pol Pot, Kmher Rouge-style takeover of the United States by facisict forces, resulting in the internment of millions of americans likely? No, not IMO.
Does the Bush admin have kooks like Bottleborne drawing up crazy contingency plans for internmnet camps? Probably. The government has kooky contingency plans for almost every possibility imaginable, regardless of how remote. We have contingency plans to invade Canada. We pay the CIA to do "studies" on how to mind-control goats. The US government wastes a lot of money doing contingency planning on all kinds of crazy stuff.
Do we, the public, need to know about it? Yes. Do we need to be on guard against it? Yes. I keep hearing posters say that the "majority" of americans would never stand for it. That's beside the point. Facsist coups are almost never supported by the majority.
I frankly think the chances of the aforementioned scenario ever happening is remote. We need to be on guard though. And I honestly think that there are simpler ways, and less risky ways, for the rightwing power structure and other authoritiarians in this country to maintain power and control the population: media consolidation, voter suppression, the slow almost imperceptible erosion of civil right (through sneaky bills like Patriot Act).
I'm a firm believer in Occum's Razor: The authoritarians in this country will most likely use very simple, low-risk, strategies that just skirt the edge of the law, to mainatin power and control. That's the easiest and simplest way to rule the country.