I've always worn a suit to interviews in the Midwest and East Coast. Once in New York (at a startup) I was told after being hired that they were concerned that I might be too stiff and strait-laced because of the suit. I did get the job, however, and I would still wear a suit interviewing there.
On the West Coast, I might go with a suit for big companies, but I'd go button down and khakis for a small company or a startup. It's a different culture. Even the better restaurants rarely require formal attire, and I feel like a suit at some interviews would show an inability to grasp the cultural differences.