I suppose it depends on your definition of "social media". The other day i heard someone say "if you're not on facebook, no-one will find your product." I suppose that depends on your market. If you're buying wide-body jets for national airlines for long-haul service, I suspect Facebook is not your first port of call. That's not an isolated example, I suspect most B2B type sales are not affected by Facebook.
On the other hand if your product is social, or the latest hip thingy, or relies on some sort of "fashion" driver (fashion in the broad sense, not necessarily related to clothing) then obviously facebook, twitter, blogging - anything at all - is good. If you're starting out, and no-one has ever heard of you then social media helps spread the word, but it'll take more than that to build something of substance.Fashion, by definition, is fleeting.Lots and lots of stuff is "famous for a day" and then sinks without trace.
Of course the author of the article is writing a blog post about blogging - to people who (by definition) read blog posts. Blogging is important for "really small businesses" to build at least some sort of profile, but it's by no means the best, or only, way to build that audience.
Those of us who "do" tech all day, every day, assume that tech is the way to solve all problems. Sometimes that's true, but in many cases not.