There's a similarity between the action that the people who work in the concessions at AT&T Park are taking and the noisy protests I saw in downtown San Francisco by security guards trying to get a decent contract. In both cases, very wealthy owners have outsourced key operations to subcontractors who don't pay their workers fairly.
You can protest outside an office building in SF, as the workers did -- but the owner of that building isn't setting your pay rate. That would be a private security company, most likely headquartered out of town, whose owners are not well known or subject to public pressure.
The Giants clearly aren't hurting for money. Two World Series victories in three years have made the team immensely valuable. Loyal fans buy three million tickets a year, selling out the place every night. The players are, of course, highly compensated.
But the Giants team doesn't hire the concession workers, who have been without a raise since 2010. That's contracted out to a company called Centerplate, a global food-service corporation. So when the workers picket at the ballpark, they're in a tough situation -- Giants management can simply say that it's not involved.
Of course, that's not exactly true: I don't know how long the Giants contract with Centerplate lasts, but at some point it's up for renewal, and if the team said today that the contract's future would depend on a settlement with its workers -- now -- that would have a huge impact. As would the support of the Major League Players Association, the most powerful union in pro sports.
In the meantime, the best way fans can show support is not to spend money at the concessions. Sure, go to the game. But don't buy food or drinks. (Ten bucks for a beer is crazy anyway).