Advertising was, for the most part, invented for traditional media (papers, radio, television). In many ways traditional media and the marketing industry are
the same thing, so bringing that up as an example of a proven business model doesn't really say much.
As far as the Internet, how many publicly traded Internet companies actually make their profits primarily from advertising? Okay, all the search engines obviously, but who else?
I just don't think you can say that ad-revenue-based models are as proven of a business model as just selling things.
