WASHINGTON — Jason Calacanis, who got into blogging early and big, has quit.

He co-founded a network of blogs called Weblogs in 2003, before the medium cracked the mainstream, and then sold it to AOL in 2005, working there until 2007. Today he is chief executive of Mahalo, a search engine guided by editors rather than algorithms.

After five years of writing on tech industry topics as well as personal ones and building an audience of 10,000 to 20,000 daily visitors, Calacanis said, he got tired of all the nasty commenters and opportunistic "link-baiters," people who post just to promote their own blogs.

So he signed off, leaving the blogosphere to others. One group that has been firing up its keyboards is corporate types. Of the approximately 112.5 million blogs on the Web, almost 5,000 are corporate, according to blog indexer Technorati. Calacanis blogged to start conversations and be a part of a virtual community, but corporate bloggers are in it for other reasons: talking directly to customers.

"It's a phenomenal promotion vehicle for a company, or a great crisis tool or a great customer service tool," said Geoff Livingston, a public relations strategist and social media expert.

Bethesda's Honest Tea launched its blog in late 2005 as a way to get close to customers. With a name like Honest Tea, chief executive Seth Goldman said, "we're trying to be as open and disclose as much information as we can." When the company announced that Coca-Cola would acquire a 40 percent interest in the brand, many of Honest Tea's customers who opposed the agreement took their complaints to the blog.

"We gave a very loud voice to the people who said they weren't happy about this decision," Goldman said.

Goldman then took one of the most thoughtful, detailed customer criticisms and responded to each point. Even if readers still didn't agree, "the blog at least helps people see how we think about it," Goldman said.

Kathleen Matthews, who heads global communications at Marriott International, thought of a blog for chief executive Bill Marriott, who saw it as a good way to communicate.

"That's the importance of public relations, of advertising, of everything we do," Marriott said. "And this is just another channel." Marriott also likes how the blog shows that he's "a human just like everybody else," sometimes breaking from writing about corporate issues to post about the movies he sees.

Marriott has thousands of employees worldwide who make up about one-fifth of the blog's readership and comment frequently. "It is the virtual substitute for Bill Marriott visiting every hotel," Matthews said.

Marriott doesn't use computers. Instead, he dictates entries into a recorder and a staff member transcribes and posts them. The audio is also on the site, which averages about 6,000 visitors per week and has had more than 600,000 total visitors since its inception in January 2007.

Marriott has made more than $5 million in bookings from people who clicked through to the reservation page from Marriott's blog.

Viget Labs, a Web consulting firm in suburban Falls Church, Va., began a blog in 2006. In his field, it's practically obligatory, chief executive Brian Wynne Williams said. "If we didn't blog," he said, "people would start to wonder about us."

The one blog has since expanded to five, each focused on a division of the company.

Wynne Williams said Viget's blogs, which target industry peers, have had a "huge impact on recruiting."

"Anybody that we've hired in the past couple of years, I think any of them would tell you that they read the blog heavily to get a sense of our people," he said.

Designer Samantha Warren said the blog sealed her decision to take a job with Viget: "The design was fantastic. It just made me feel like I want to be part of something this good."

Smaller businesses are experimenting, too, since a blog can be an economical way of getting attention.