On the Web, there is very little differentiation between types of content.
People don't really care where they get the best content: mainstream media, content created by organizations (what I call brand journalism) or things that people share via social media.
Arguing that one is more legitimate (mainstream media) leads to flawed marketing and PR strategic decisions.
In an offline world, marketing and PR are usually separate departments with different people and different skill sets. Creating silos in companies for marketing and for public relations and for social media doesn't work when creating attention on the web and mobile. It's all content.
Reaching buyers on the web and via mobile
When a buyer is researching your product category by using a search engine, does it really matter if the first exposure is a hit on your website, a news release your organization sent, a magazine article, or a post on your blog? I'd argue that it doesn't matter.
The distinctions have nearly disappeared.