After the 2000 Census, the richest county in America was Douglas County, Colorado. By 2007, Douglas County had fallen to sixth. The new top three are now Loudon County, Virginia; Fairfax County, Virginia; and Howard County, Maryland. All three are suburbs or exurbs of Washington, D.C. In 2000, 14 of the 100 richest counties were in the Washington, D.C., area. In 2007, it was nine of the richest 20.
My guess is that there is a pretty strong relationship between the share of government spending in GDP and the share of incomes in the DC area. Since the former is going to rise dramatically in the coming years, the latter will, too.
If you thought it was unproductive for the best and brightest to go to Wall Street to become investment bankers to decide to use other people's money, watch what happens when the best and brightest come to Washington to decide how to use other people's money.