I agree, I don't know much about digital marketing but I know that anecdotal evidence, which is all the author is presenting, is next to useless. I've heard other claims from people about how they made enormous sums on facebook.

The real issue is that neither of these claims constitute data. Only large scale research tracking traffic across many websites would let us come to meaningful conclusions and that sort of research is something I haven't seen yet . . . which is likely why we are stuck with all these he said she said stories about how social media is a useless moneysink or a veritable gold mine depending on who you ask