[LeoSolaris]

It keeps the unqualified from swamping HR. That and they are good for minimal skill/experience jobs to dredge in the most number of applicants. It is for high risk hiring where the job is not cared about as much so if the employee is a bad apple, it isn't of high impact to the company.

I've never once found a decent job off of anything other than a personal referral or internal posting. This is for finding skilled individuals who already have industry experience and reputation. It isn't supporting the "Good ol' Boys" so much as a way to gauge potential employees based on those around them. Who you know is a reflection of your value because good people are valued by those around them.

Head hunting on the other hand... that's an entirely different animal. That one depends on the quality of the headhunter more than anything else.