With the general experiences, it's very hard to understand what the interviewers think. For example, interview result is never revealed. Giving the ideal answers to the questions is never easy, especially the questions were designed to locate the expereienced candidates. Plus it always has candidates have more working experiences and possess much better background to the position.
Another situation is people answer most questions and the whole interview is going very smoothly, but after one week, there is still no following up emails or phone calls. At that moment, the only thing shows out is frustrated.
The reason that job is not offered is often the candidate, who is the one can break such unemployed phase but forced interviewers to change their decision. "God helps those who help themselves." Wish every job seekers find your dream job.