When I got my BS degree in business administration last year, my advisor told me to make sure I attended the university's annual job fair. I'm glad I did, because I managed to get a personal interview with a company I've had my eye on for years. I got called back for a second interview a few weeks after the job fair, and now I'm working as a small business consultant for their Chicago office.
The thing I noticed about job fairs is that different companies have different agendas. Some are actively seeking to recruit talent, and they will do things like personal interviews and one-on-one lunch meetings. Others are mostly trying to fill up their application bins, but they know they're not actively hiring at that time. A few are there just to let potential applicants know they exist, but not much else.