Are Job Fairs a Waste of Time?

As a recruiter, I am asked to participate in job fairs all the time. Unless it is one where my community is involved, I rarely attend. Why? Because the odds of the perfect candidate stepping forward for a current job I'm trying to fill is pretty low. Why, then, don't I go just to meet candidates for future opportunities? Because by the time I might have a job for them, they likely would have been hired elsewhere. Plus, I do this throughout the year with more targeted networking.

Many other hiring managers feel the same way. If the fair is very specific to my industry or jobs, there is a greater potential; but in general, job fairs bring in as many job seekers as possible. So, should job seekers go to job fairs?