Dan Schawbel at Stepcase Lifehack writes an article discussing on company rights to block or not access to social sites (and among them to blogs), with special attention on what is about possible use of this type of communication (full article at http://www.lifehack.org/articles/management/does-your-company-support-your-blog.html).
In my opinion is not a problem of freedom nor of possible uses.
In a company, especially those with a strong identity (on brand and communication side), executives could want to have strict control on which messages are given to public and which is the way they are addressed.
For me nothing is taken from personal freedom if access to some (or all) social sites is blocked or restricted because people take money for doing work, not for using social networks. And at least is a problem of business ethics: even if everything I said is questionable, is a problem of talking about a company internal facts that should not be allowed.
I think that everybody gives as obtained the right of using internet for doing something that is completely or partially unlinked from work: it’s not a right, is an opportunity given by companies that pay the costs.
This post as a comment also at http://www.lifehack.org/articles/management/does-your-company-support-your-blog.html/comment-page-1#comment-342229