A growing number of supervisors are writing about their lives, friends, and jobs on a personal Web log, or blog. Blogging material is a mix of commentary, opinions, and photos.

Because of concerns about trade secrets, libel, and poor taste in material, many firms are enacting guidelines. Companies including Goggle and Delta Airlines, and Cold Stone Creamery (see article here) have fired or disciplined employees for what they said about work on their blogs. Employers such as IBM now have published guidelines for bloggers.

At the same time, companies don’t want to stifle the kinds of blogs that create a positive and valuable buzz about the company.

More than 8 million adults in the U.S. have created blogs, according to recent surveys. Last year, about 32 million Americans were blog readers, a 58 percent jump from the previous year, and the number is growing.

Bloggers can communicate about their companies directly with the public. But according to USA Today, bloggers have been known to reveal trademark or copyright material, post pictures of products in development, and slander another worker, boss, or client.

Most guidelines say bloggers should not use ethnic slurs, personal insults, or obscenity. Writers should show proper consideration for topics that may be considered objectionable or inflammatory such as politics and religion.

Civil liberties organizations fear the guidelines may stifle the free exchange that has made blogs so popular. Most employees, however, think the policies are good. They want to know whether they are breaking the rules.