Twitter did get a tax break to keep their office in SF. [See here](http://latimesblogs.latimes.com/technology/2011/04/twitter-g...)
> The payroll-tax break could lead to Twitter saving about $22 million in taxes over six years, the Chronicle said.
I think the gamble was the city would make this back thanks to revitalization or new workers moving into the city. In the near term, there's certainly going to be a reduction in the city coffers for taking care of punchy-guys.