Here's a great piece by Charles Fountain, focused on the Grapefruit League. One highlight is the exchange of verbal blows between USF's Phil Porter and a local promoter. Porter wins on points, as the promoter trots out the seeing is believing fallacy, which always overstates the impact.
Here is where Porter nails it:
The only way to be certain of its real impact, Porter believes, is to look at what happens when spring training goes away. “Wait until somebody moves,” he says. “These are the things that provide natural tests for whether or not spring training provides the economic kick it is said to provide. If a team moves out of Winter Haven, say, what happens to Winter Haven? If next year it’s business as always with the same sort of sales and income and employment, then you gotta conclude that the presence of the team didn’t add anything to the community, because its absence didn’t take anything away.”