I think the first time I noticed social marketing was a few decades ago when a phone company started offering friends and family discount plans. These, from the point of view of the firm, were clever because the locked the customer into a plan, since switching would need explaining to your friends and family why you were abandoning them.
Another famed example of social marketing was the viral marketing used by Hotmail. Customer emails were infected with advertising in the hope that their correspondents would thing the customer was providing a product endorsement.
So here’s a new one. Verison’s Fios division has an Ad running with the tag line “Is it you?”. Pairs of customers ask this of each other with the implication that one of them is failing to provide a high quality relationship because she hasn’t signed up for Fios. Shame on her!