You're right to read widely about companies that interest you. You're productive when you follow blogs that cover new developments in the industries you're investing in or considering. But before you take everything you read for granted, consider your sources' potential biases. The mainstream media isn't always as independent as you think, and some of the blogs you may be enjoying could come straight from a company's PR department.

PepsiCo (NYSE: PEP), for example, operates the Food Frontiers Blog, where its experts discuss nutrition. To be fair, the Pepsi connection is made clear at the top of the page. The blog's support for healthier eating is laudable, as are the company's efforts to reduce added sugar and other problematic ingredients in its offerings. But an 11-ounce bag of classic Lay's potato chips (which many people consume in a single sitting) still holds 110 grams of fat and nearly 2,000 milligrams of sodium. Clearly, however healthy an image its blog promotes, Pepsi is not all about nutritious fare yet.

Even more troubling are corporate blogs such as the (now retired) Brew Blog, which was operated by Miller Brewing (now SABMiller). It tended to discuss and diss competitor Anheuser-Busch InBev (NYSE: BUD) to an unusual degree -- hardly an objective viewpoint.

The benefits of corporate blogging are clear -- for the corporations, at least. They get to disseminate the information and messages they choose. If their blog catches on, they'll attract regular readers to their website.

Admittedly, some corporate blogs can also serve readers well. The Garmin (Nasdaq: GRMN) blog caters to active consumers and travelers, offering updates on new GPS products and technology, as well as topics such as bike races, road trips, and speed golf.

The bigger picture
Blogs aren't the only media sources owned and controlled by major corporations. Check out the noted news and publishing outlets that fall under the umbrellas of these publicly traded companies:

  • Disney (NYSE: DIS): ABC, ESPN.
  • News Corp.: The Wall Street Journal, Fox television, MarketWatch, Dow Jones News Wire.
  • General Electric (NYSE: GE): NBC, CNBC, MSNBC. (GE plans to sell a majority interest in its NBC Universal to Comcast.)
  • Time Warner (NYSE: TWX): CNN, TIME magazine, Sports Illustrated, Fortune, People.
  • CBS (NYSE: CBS): CBS, Simon & Schuster.

Conflicts of interest abound, and it's not hard to imagine news personnel in these organizations being restricted in what they cover or influenced in how they cover it.

Whenever you receive information from the media, keep the ultimate source in mind. And remember, even biased communications can be valuable, by revealing what a company wants us to focus on.