I once got two raises in an interview because I was so (pleasantly) surprised by the size of the first offer that I wasn't sure what to say. There was a bit more to this situation - I liked the job I was in and the employer really needed someone, but it was still a revelation.

Keeping your mouth shut, saying no, and not lying or BSing are three of the most useful skills you can develop. Many people feel pressure to respond quickly, especially in a performance situation like an interview, just as the writer of this article was highly tuned to what his interviewer wanted to hear. Controlling the tempo and direction of your own responses is a way to gain the strategic initiative without being disagreeable.