Here was an update 8 weeks after the original Panera Cares location was opened (http://blogs.reuters.com/
Interestingly, each of the these locations have a lower median income than Clayton and they are more heterogeneous along other dimensions.For example, Dearborn is the capital of the Islamic Center for America and has a large Arabic population. Portland, Oregon is not racially diverse however they are more secular than Clayton or Dearborn. The notion of heterogeneity and secular matter because they have shown to correspond to less trusting or charitable behavior. The lower income levels of these cities also make them a very interesting experiment compared to Clayton, MO (they are homogenous and wealthy as written in an earlier post).
I guess the question still remains. Giving to charity seems easy, but, difficult when your stream of revenue from donations is uncertain. If warm glow can work through identity or existence value how do you generate that in your customer base?