Why campaign donations should be secret

There is a real cost to making campaign donations public.  Take an example from this week: 

Mozilla -- most famous for its Firefox browser -- patted itself on the back for standing up for equal rights when it forced out CEO Brendan Eich Thursday after only a week on the job.
The Mountain View, Calif.-based organization infuriated many employees and users last week by promoting Eich. The hullabaloo centered on Eich’s $1,000 donation in 2008 to support Prop 8, the California initiative that barred same-sex marriage in the state.
The dating website OkCupid, which says 8 percent of its users are gay or lesbian, boycotted Firefox earlier this week, telling its users not to use Mozilla's software to access the site in light of Eich's promotion. . . .

Imagine the impact that public information on donors could have on the willingness of people to make donations against powerful politicians.