Separating social media from sales-focused websites?

The first bullet-point on this blog post suggests that blogs (and, presumably, other social media venues) should be separated from sales-focused websites. The argument seems to be a good one -- "The focus of the .... blog is on engagement, not marketing."

http://smartblogs.com/socialmedia/2011/04/28/andys-answers-how-scholastic-developed-their-corporate-blog/