It will stimulate the economy! Wash Post:

As the first same-sex couples married in Washington on Tuesday, the city is in the national spotlight as a pioneer in the gay-rights movement. But local officials say the historic event also has more practical implications for a city grappling with 12 percent unemployment: jobs. A study by the nonprofit Williams Institute predicted that legalizing same-sex marriage will create 700 jobs and contribute $52.2 million over three years to the local economy.

UPDATE: E-mailbag:

Ah, but what about the carbon footprint involved?
“The bigger windfall is expected to come from out-of-state couples — particularly from New York — seeking to get married in the nation’s capital. The report estimated 12,500 such couples would travel to the District in three years….”