thoughtfulA little searching finds that the Reno-Sparks Metropolitan Statistical Area had 410,272 people in 2007. I thought that possibly Brighton, with a listed population at about the same time of 251,400, might beat it; however, you have to use comparable terms. An MSA is the county (or counties) in which the named cities are located (in Reno-Sparks' case that's Storey and Washoe counties, Nevada). The equivalent for Brighton is East Sussex, which has a claimed population of 752,900. Winnipeg might also be in the running -- its metro area is listed as 694,668.
Maybe other people can look over the Long List of Worldcons and do more research, but after my first pass, it does appear that the 2011 Worldcon is probably going to be in the smallest metropolitan area to ever host a Worldcon. The facilities there certainly aren't small, however. I'd be more comfortable if there was one more large hotel directly on site rather than a kilometer away, but there's plenty of convention center space; more than we'll need, I'm sure.
