We know the inverse is true. Any information that is shared becomes a social piece of content.
But what makes something "marketing?"
Is it the intent when the user or business posted the content? This would be easy to decipher if it weren't true that it's not up to the publisher to make something shared.
So shared = marketing in motion.
Forget about intent or origin of the content. Anything that's shared is social. And anything social is posted for marketing purposes.
That said, does social equal shared?
I guess it depends on who is the one sharing it.