Blogs have had an impact on traditional journalism, politics, business — just about everything fundamentally important to our democracy. It was only a matter of time before someone created a whole new industry dedicated to the business of blog watching.

Remember the “markets are conversations” post I wrote yesterday? Here’s an illustration of the concept in the Wall Street Journal:

Blog watching helped advertising giant WPP Group PLC craft a new promotion aimed at teenagers for its Chicago-based client U.S. Cellular Corp., says Bethany Harris, senior vice president of WPP’s G Whiz Entertainment unit…..

Marketers say bloggers’ unsolicited opinions and offhand comments are a source of invaluable insights that are hard to get elsewhere. “We look at the blogosphere as a focus group with 15 million people going on 24/7 that you can tap into without going behind a one-way mirror,” says Rick Murray, executive vice president of Edelman, a Chicago public-relations firm….

Blog-monitoring services typically charge big companies $30,000 to $100,000 a year. They say their technology goes beyond basic tools, such as keyword searches or counting links from one Web site to another, both features available at no charge from online services such as Technorati.com and Yahoo’s Buzz Index.

The power of blogs can’t be overstated. If you’re not blogging for your business or at least listening to what bloggers are saying, you’re missing out on a valuable market.