The Cato Institute has released a study showing that a city-financed baseball stadium will have no economic benefit to the District (mostly because money spent there will be diverted from other places of entertainment) and possibly will be an economic detriment. Cato's study also argues that building a stadium will detract from efforts to end the War on Drugs. (Only kidding about that last one.)
About all of this I have one word: DUH! The folks who run D.C. are a bunch of suckers, but I'm glad they are, since I can see the games and don't have to pay for the stadium. (We Marylanders are stuck with the Glendening-Modell fiasco, which is pretty awful, too.)
Previous posts on the move of the Expos to D.C. are here, here, and sort of here.
UPDATE (10/29): The Wall Street Journal weighs in:
Mayor Williams has already mocked Cato for bothering with the study. And there will always be folks who remain willfully blind to the high costs and associated idiocies of publicly financed stadiums. In such contexts, "corporate greed"--team owners raking in millions from naming rights, luxury boxes, club seats, etc., at a stadium built for them--doesn't bother sports boosters. Their hearts want what they want.