The Comptroller General of the United States, David Walker of the GAO, writes:

The Roman Empire fell for many reasons, but three seem particularly relevant for our times: (1) declining moral and ethical values and political comity at home, (2) overconfidence and overextension abroad, and (3) fiscal irresponsibility by the central government. All these are certainly matters of significant concern today. But it is the third area that is the focus of my responsibility and authority as Comptroller General, the nation's top auditor and chief accountability officer.

Unfortunately, there is no question that both U.S. government spending and tax cuts are spiraling out of control. Recent increases in federal budget deficits have far outpaced the cost of the global war on terrorism and incremental homeland security costs. Although the $319 billion fiscal 2005 deficit was considerably lower than the previous year's, it is still imprudently high -- especially given that federal spending is expected to increase dramatically when the baby boomers begin to retire later this decade.

Recommending this quote from DailyKos because I don't want to link to the registration-required BusinessWeek article.