Much is written about networking as the primary job search tool. Personally I think it is overrated and prevents people from doing any sort of cold calling on their own. But that's ok. If candidates really learned how to conduct a job search recruiters would be obsolete pretty quickly.
A lot of companies do hire via internal referrals however so it is wise to keep track of where your friends are.
One example is an outfit called Corporate Executive Board which recruits aggressively for MBA's from some of the finest B schools in the US.
Wendy Person who is the Senior Director of Talent Management tells Businessweek that those who want a job with their company had better work their network:
More than 40% of all hires come from internal referrals. If candidates aren't networking with alumni here at CEB, they are missing out on a wonderful opportunity.
Of course that's assuming they want to work at a place with a lame name like "Corporate Executive Board". Was "Company Limited Incorporated" already taken?