Consumption tax drawback
People "tighten their belts" during economic downturns. Even people who are not afraid of losing their jobs still cut back on non-essential purchases. This leads to a drop in sales tax revenue and deficits.
Washington state has a sales tax instead of an income tax. Last time I checked we were 1.5b in the hole and set to raise taxes to recover.
Maybe a good tax structure would some how sparingly modulate the swings in the economy. You could ease the tax burden a little during a crunch and rake a little more off the top during boom times.
Now if only there was someway to keep governments from spending surpluses...