Forbes has their list of baseball's most valuable fans. Here's how they figured this out:

In our first ranking of the most valuable fans of MLB, we flipped tradition on its head and took a look at what audiences around America are worth to the business of baseball. We divided local revenue of each team (including such sources as local television and radio revenue, gate receipts and sponsorships) for the 2008 season by the population of its metropolitan area, according to the 2008 U.S. Census Bureau estimate. The resulting revenue-per-fan figure is a rough yardstick of a team’s ability to capitalize on its fan base, regardless of market size.

Revenue figures are before revenue sharing and exclude national media and licensing revenue, which is divvied up equally to all 30 MLB team. For cities with two teams, we divided the population in half for each team, figuring the city’s fan base was split more or less evenly between the two.

Using this methodology, they came up with being worth $45 each. The top of the list was the Giants at $78 and the bottom was the Marlins at $11.

Via Steve Lombardi.