I trust Gerry Crispin. So should you. He is not a career branding "expert" or any other type of new media blow hard. He has data. Real data. Dare I say "Big Data"? He doesn't make up stats and figures to promote his business.
Why do I bring this up? Well - it seems some people in the "how to network" coaching business want you to believe that 80% of the job openings are being filled through networking. And where does that stat come from? Who knows....? Not Gerry Crispin.
Where does Gerry get his info? From 35 GIANT companies that (combined) filled 1.2 million + vacancies last year. I'd call that "substantial"? Wouldn't you?
I found the info on his site - Career X Roads quite informative. Take a look under the "Resources" tab - and you'll find this survey under Articles.
(In case anyone wants to know how companies really hire people)