I don't think that most interviewers remember that candidates will be weighing every word that they say, looking for positive or negative "signs," and therefore, they don't really think about how their statements will affect candidates. For example, at my former company, I was part of a two-person interview team interviewing recent graduates for entry-level positions. We were talking to one candidate with unique language skills and my co-interviewer kept raving about how great these language skills were and how valuable the candidate would be - to the candidate's face. However, the language skills weren't going to override some other missing qualifications necessary to be hired - something my colleague knew but was apparently just not thinking about in the interview. I don't think my colleague meant to mislead the candidate or imply that a job was all but guaranteed; I think he just wanted to be encouraging and emphasize that the candidate should really try and sell those skills, because we did really like the candidate as a person. Unfortunately, I think the candidate left with a definite impression that a job offer would be forthcoming, and we ultimately had to reject him.
If I could have kicked my co-interviewer under the table to get him to stop talking, I would have. Like I said, there was no deliberate attempt to mislead the candidate - he just wasn't thinking about the effect of his statements. Unfortunately, I think a lot of interviewers are like this and I really don't think you should overanalyze what they say in the interview. Now, if they tell you straight out that you have a job offer, well that's a different story.
Good luck!