Nearly one in four businesses block employee access to social networking Web sites such as Facebook and MySpace,according to a survey of about 200 human resources professionals.

With the number of Americans using social networking sites tripling in recent years, use of such sites has grown during work hours. People ages 35 and older are using MySpace and Facebook in droves.

"Many companies look the other way," but others view social networking as a "productivity killer," says Challenger, Gray & Christmas, a consulting firm that surveyed human resources pros at a recent conference hosted by the Society for Human Resource Management.  

"While many companies do not view social networking as a threat to productivity, one in three survey respondents said their companies consider the sites a major drain on worker output," Challenger says. "Twenty-three percent of companies block access to these sites entirely."

Eight percent of companies actually encourage employees to use social networking sites, and 10% say they are invaluable marketing, networking and sales tools. Banning use of sites could also make it hard to recruit young employees.

To get a real recruiting edge, business should integrate social networking and other Web 2.0 tools "into every facet of the organization, from marketing to internal employee communication," Challenger says.

Most companies aren’t formally addressing social networking sites. Fifty-nine percent do not have a formal policy on using the sites during work hours. Nearly half said social networking isn't a problem as long as employees get their work done.
Formal corporate policies on social networking are scarce because it is such a new phenomenon, Challenger, Gray & Christmas say, noting a Pew Research survey that found the proportion of Americans using such sites has risen from 7% to 22% since 2005.

The Challenger firm also quoted a study from U.K.-based IT security firm Global Secure System, which said employees are spending 30 minutes or more per work day on social networking sites. Viruses and leaking of confidential data are among the dangers raised by heavy usage. (Compare security products.) 

"Lost productivity is not the only reason some organizations ban or limit the use of social networking at the office," the Challenger firm states. "These sites produce an extra demand on bandwidth. They also pose a security risk for corporate networks, making company systems vulnerable to hackers and viruses. There is also the potential for employees to leak corporate secrets or damage the company’s image due to the content of their personal profiles."