Should bloggers be free to criticize their employers in their posts? Most bosses would say no. And most bosses could be wrong. "Under certain conditions, negative postings by employees can actually help the overall reputation of the firm" says this paper (pdf).
This is because such postings attract more attention and page views than bland pro-company posts, which means that subsequent, positive posts get more attention. What's more, because the employee is free to post bad things, these positive posts are more credible.
The authors establish, with some cunning stats, that Sun Microsystems' liberal blogging policy actually helps the firm.
Which raises the question. Why then, do many firms limit worker-bloggers?
I suspect that, for quite a few bosses, what matters is not that their company be presented in a positive light but rather that they have control over their firm's image. Power matters more than efficiency.