(FORTUNE Magazine) – JONATHAN SCHWARTZ, PRESIDENT AND COO of Sun Microsystems, has recently criticized statements by Intel executives, mused that IBM might buy Novell, and complained about a CNET.com article--all by writing a blog on a Sun website.

Yep, blogs--which are a way to post text to a website--have found their way into business. Schwartz is the highest-ranking executive yet to embrace the new medium, which is burgeoning globally. About 35,000 people read his blog (http://blogs.sun.com) in a typical month, including customers, employees, and competitors. Schwartz encourages all Sun's 32,000 employees to blog, though only about 100 are doing it so far. But they include at least three senior managers other than Schwartz as well as development engineers and marketers.

The company's most popular blogger is a marketer known as MaryMaryQuiteContrary. Her blog ranges from rhapsodies about "proxy-based aspect-oriented programming" to musings about her desire to become a first-grade class mother. Says Schwartz: "I don't have the advertising budget to get our message to, for instance, Java developers working on handset applications for the medical industry. But one of our developers, just by taking time to write a blog, can do a great job getting our message out to a fanatic readership." He adds, "Blogs are no more mandated at Sun than e-mail. But I have a hard time seeing how a manager can be effective without both."

Over at Microsoft, some 1,000 employees blog, says a spokesman, though no top executives do. Robert Scoble, Microsoft's most prominent blogger, says via e-mail that "I often link to bloggers who are not friendly to Microsoft. They know I'm listening, and that alone improves relationships." Other tech companies with company blogs include Yahoo, Google, Intuit, and Monster.com. Even Maytag has a blog.

But businesses are learning --sometimes the hard way--that this new medium has pitfalls. David Farrell, Sun's chief compliance officer, notes that the company will soon require employees to agree to specific guidelines before starting blogs. Companies are also worried about unflattering portrayals and leaks. Last year a Microsoft contract employee posted a photo of the company receiving a dockful of Apple computers; he was promptly fired. A Harvard administrator and a software developer at Friendster were also recently fired after personal blog postings. (Microsoft, Harvard, and Friendster declined to comment.)

But some managers find that even more important than writing blogs is reading them. During a recent conference for Microsoft software developers, top company executives huddled backstage reading up-to-the-minute blogs written by the audience to get a sense of how their messages were being received. -- David Kirkpatrick