An interview is a two-way street. I've walked away from two interviews because the whole ordeal was going to be very time consuming and I just wasn't sold enough on the company.

I did do two coding exercises, though. In one case, the exercise was very fun, and I was able to use it as an excuse to work in a language that I didn't work often in. In another case, I really believed in the company, but I would only do something that took about 1-2 hours.