Maybe default is called disastrous because it leads to Moody and others lowering our national credit rating. I am not exactly clear why this is bad, but I know when my personal credit rating falls I have a harder time affording higher house payments and buying a car, among other things.
The Laffer curve has been proven, time and again to be spot on. Cutting taxes DOES bring in more revenue. Unfortunately, no matter how much money the Government takes from us, the always spend more than take.