It seems innocuous enough at first. A user claiming to represent Exxon Mobil on micro-blogging site Twitter highlighted this post from August 2, "Did You Know? We supported local NGOS (non-governmental organizations) in Angola and Indonesia to develop their capacity to effectively partner with multi-national companies" on a Twitter page dotted with the Exxon Mobil name, logo and photos of Exxon gas stations. More than 300 people have signed up for regular updates from Exxon on Twitter since July 28, when posts purportedly from the company first appeared.

But the user posing as "Janet" from ExxonMobil and posting what appeared to be legitimate "Tweets" is not authorized by Exxon Mobil to be posting about the company. Exxon Mobil does not know who "Janet" is or if he or she is even a company employee, Exxon Mobil spokesman Alan Jeffers said Monday.

"She is not an authorized person to speak on behalf of the company," he said. "There are several inaccuracies (on Twitter). We take great care in having authorized people speak on behalf of the company. We want to make sure anyone who is speaking for the company is doing so accurately."

The company plans to contact Twitter because some of the photos used by "Janet" are copyrighted material, used without authorization, he said. While Exxon Mobil has "no problem" with those who might criticize the company, it does object to anyone doing so anonymously. "We think it's important that people are transparent and honest about whom they represent," Jeffers added. "We think they should be honest about where they are coming from."

Exxon Mobil itself is not using Twitter, nor any other social media forum to communicate about its corporate operations, he added. But the tool - which allows users to post 140-character or less mini blogs, has become increasingly popular among some enterprises. Some businesses have used Twitter as a way to monitor customer comments and complaints, while some members of Congress have been Tweeting from the floor about votes and issues. NASA's Jet Propulsion Laboratory has been posting Tweets about its Phoenix Mars Lander project.

Some of the posts from "Janet" seemed to favor the corporate marketing messaging often found on social networks. For example, "Janet" said in an Aug. 1 post that "I believe we are the first major energy company here (on Twitter). Exxon Mobile is trying to lead the way in corporate citizenship." And on July 29, "Janet" posted this: "Exxon Mobil reduced its Greenhouse Gas Emissions by 5 million metric tons from 2006 to 2007!"

But other posts on Twitter were more controversial. On July 29, Janet responded to a question by another Twitter user noting, "Although the Valdez spill was tragic, it was only 10 million gallons. Compare that to the 73 million in the Nowruz Oil Field in 1983."

Jeremiah Owyang, an analyst who covers Web 2.0 technologies and issues for Forrester Research, noted that "Janet" has "brand jacked" Exxon because the company was not monitoring and responding to how its brand was being used and talked about on the Web.

"Brands should be monitoring the discussion and instances of their keywords in social networks -- failure to do so results in becoming case studies," he noted in a blog post. "The power has shifted to those that participate, so while Janet may have achieved momentum by participating, further opportunity lies within Exxon when they're ready to come forward."

Shel Holtz, principal of Holtz Communication + Technology, a consulting company for corporate communications on the Web agreed that the Exxon Mobil incident on Twitter should be a wake-up call for companies not paying attention to social media space.

"Any company should be acquiring the Twitter account names that are most likely to be construed as official accounts," he noted. "Far too many organizations shrug off emerging social media channels like Twitter and Friendfeed. The Janet incident should make it painfully clear just how easy it is for somebody to step in and represent your organization with inaccurate and even damaging information using these very channels."