I've just come across a paper published earlier this year on employee blogging.

General details can be found here.

Some details of the study (provided by Business Wire):

The authors looked at bloggers in Fortune 500 IT consulting and services companies that permitted both leisure- and work-related blogging, and studied work environments where the company prohibits leisurely blogging.

They found that when organizations put restrictions on leisure blogging, online work-related knowledge sharing decreases.

The authors believe this happens because creating social media content at work not only helps employees to educate those seeking information, but also helps them build social relationships in the workplace.

An employee can attract fellow employees to his blog with an entertaining or leisure post and, because work-related posts are on the same page, there is a spillover effect with people reading work-related articles.

The actual paper can be found here: A Structural Model of Employee Behavioral Dynamics in Enterprise Social Media by Yan Huang, Param Vir Singh and Anindya Ghose.