Minor league baseball is returning to Richmond, as the AA Connecticut Defenders will move there next year (H/T Sabernomics). Richmond for a long time had the AAA franchise of the Atlanta Braves. Before last season the team moved to Gwinnett County in exurban Atlanta. One advantage of this move was that having a AAA franchise nearby is advantageous to the major league team, since AAA players are often being called up to the major league team. However, the major issue was that Gwinnett County agreed to build a new stadium, while the park in Richmond was "old" (1985). J.C. at Sabernomics has covered the issue extensively over the last year (see here, here, here and many more).
A few years ago (data from 2003, published in 2006) I did a study looking at the relationship between minor league baseball team locations and various factors (population, income, distance from major league teams, etc.). However, it does not include stadium age or quality, which I was treating as an endogenous factor, i.e., a large city will have more resources to invest/waste on a ballpark. Over time baseball teams have distributed themselves very efficiently with few outliers from the predicted pattern. Table 6 of my paper presents the biggest outliers for AAA, AA, High-A and the metropolitan areas with no teams. According to the model, Richmond should have either a AAA or AA team (leaning towards AAA). If Richmond did not have a team at the time of the study, it would have been 5th on the AAA list and 1st on the other three. Richmond with no baseball team is clearly underrepresented by baseball.
Regardless of the stadium issues associated with the Richmond Diamond, the appeal of the Richmond market relative to Norwich, CT was too much for the Defenders' new ownership to ignore. Richmond's metropolitan area population in 2007 was 1,211,101, while Norwich's was 263,770. An additional one million potential fans can make up for a large number of other problems.