More recruiters are relying on Facebook, LinkedIn and other social media sites to fill job openings, with few candidates coming from staff referrals, according to Jobvite.

In a recent survey of 115 human resource managers at small technology firms nationwide, 64 percent said they're tapping into online social networking to find job candidates, the San Francisco-based employment firm said. Many recruiters said they planned to make even better use of social and professional networks in the future.

By contrast, 80 percent said less than half of all new job candidates were referred by current employees. Despite spending up to $25,000 a year on referral bonuses, most employers said referrals account for only a small percent of new employees, the survey found.

"A lot of times companies don't have systems in place to track referrals in a good way," said Jobvite founder Jesper Schultz. He added that referrals were the most reliable way to find new employees.

"When you put out a job ad on a job board, how do you figure out who's good and who's not good?" Schultz said.