This NewYork Times article discusses about the problem faced by an intern of Comedy Central. Following is a passage from that article:
"Viacom, the parent company of Comedy Central, now has an explicit policy. In a section on confidentiality, it states that the employee is "discouraged from publicly discussing work-related matters, whether constituting confidential information or not, outside of appropriate work channels, including online in chat rooms or 'blogs.' ""
Some other companies/organizations that have/had no blogging policies are:
1) Olympic Sports 2004
2) Apple Retail Division (blogs discuss this, but I could not find any confidentaility agreement of Apple Retail Division)
Please drop a line if you know any of such companies.
Following are some of the blogs/websites/wikis that discuss about the culture of corporate blogs: