More than 22 million people in the U.S. used social networks to find their most recent jobs, according to a new study from job recruitment site Jobvite, up from just 7.7 million last year.

Further, one in six workers revealed that a social network was one of the sources they’ve used in their job search. Overall, 54 percent of those polled for Jobvite’s Social Job Seeker Survey 2011 said they’ve used Facebook, LinkedIn or Twitter (News - Alert) to seek work.

Among the three major social networks, Facebook has the greater number of job seekers at 84 percent of those polled. Twitter is next on the list at 39 percent, followed by LinkedIn at 35 percent. Almost one third (31 percent) of the respondents have an account on all three networks.

But Facebook (News - Alert) isn’t getting as much use as it could. More than one-third of the job seekers surveyed that have a Facebook profile aren’t using it to find work. But almost all of those with LinkedIn (News - Alert) profiles and three-quarters of those with Twitter profiles are using their accounts to look for a job.

Drilling down further, a full 48 percent of all job seekers (and 63 percent of those with a profile) have gone job hunting on Facebook. One out of every five job seekers added professional information to their Facebook profile over the past year. But only 16 percent got a job referral from a Facebook friend.

In comparison, 26 percent of all job seekers (and 88 percent of those with a profile) have used LinkedIn to look for work. Only 15 percent of LinkedIn users have updated their professional information, and only 9 percent have received a job referral from a contact on the network.

And 23 percent of all job seekers (and 71 percent with a profile) have used Twitter to search for a job. Only 8 percent have updated their professional information on Twitter, while 6 percent have gotten a job referral via Twitter.

“Our new national survey shows that socially savvy job seekers have an advantage over their fellow job hunters and it's paying off,” said Jobvite President Dan Finnigan. “While referrals are still the top source of new jobs, online social networks play an increasingly important role in job hunting today. The job referrals happening on Facebook, LinkedIn, and Twitter benefit employers, job seekers, and the economy overall.”

I think Finnigan’s comment about referrals is important. Social networking should not take the place of face-to-face networking or other resources when looking for work. Real contact with other people is still the best way to find the right position. But job seekers need to take advantage of all the resources available to them. And as social networks continue to grow in membership and popularity, they should be one of several important sources for any job search.

Conducted on behalf of Jobvite from October 24 to 27, the poll reached 2,049 adults, 1,205 of whom are currently part of the American workforce.