Yeah, I'm not talking about individual choices to do or not do business with those companies you … umm … choose.
I'm talking about coordinated boycott efforts. Either they're going to blow up in your face and draw more business (Chick Filet is a grand example of that), or you run the risk of tossing folks out of their jobs and creating undue burden for average folks. I did a quick search, and the consensus is that boycotts hurt the wrong people, i.e. the employees and customers, not the super rich corporations.
They're ineffective for everything but two things: Adding to unemployment, and padding the egos of boycott organizers. That's all they do.