Your observation is a good and material one. Not everyone will be as observant. As such, it's up to publishers to be as transparent as possible to distinguish reportage from opinion, paid content from more traditional editorial, contributions from staffers "vs" non-staffers, and what represents the voice of the publication "vs" individual contributors (regardless if they're staff or otherwise). IMO, the industry has work to do here - and Forbes is doing a good job of it so far.

(I work at Forbes; my opinions are my own.)