Companies block Facebook: Social networking sites considered to be bad business

A growing number of employers are refusing to be Facebook's friend.

Companies around the world are increasingly choking off their employees' access to social-networking websites, such as Facebook, Twitter and MySpace, says ScanSafe, one of the Internet's biggest security providers.

In the past six months alone, there's been a 20% increase in the number of companies blocking such websites, says ScanSafe, which released a study on the phenomenon this week.

"When web filtering first became an option for companies, we generally saw them block access to typical categories, such as pornography, illegal activities and hate and discrimination," said ScanSafe spokesman Spencer Parker.

"I imagine, before long, social networking will be up there with pornography in terms of categories blocked."